Document CLI commands

[melissawm]

Right now, only a couple of commands are documented/have docstrings. We should add some documentation to differentiate e.g. ascii from browse, render from serve...

$ papyri --help
                                                                                                                                                                                          
 Usage: papyri [OPTIONS] COMMAND [ARGS]...                                                                                                                                                
                                                                                                                                                                                          
 Generate Rich documentation for IPython, Jupyter, and publish online.                                                                                                                    
 Generating Docs:                                                                                                                                                                         
 To generate documentation IR for publishing.                                                                                                                                             
 $ papyri gen examples/numpy.toml                                                                                                                                                         
 Will generate in ~/.papayri/data/ the folder `numpy_$numpyversion`.                                                                                                                      
 Ingesting Docs:                                                                                                                                                                          
 To crosslink a given set of IR with current existing documentation IRs                                                                                                                   
 $ papyri ingest numpy_$numpyversion [....]                                                                                                                                               
 Generating standalone HTML for all the known docs                                                                                                                                        
 $ papyri render                                                                                                                                                                          
 To start a server that generate html on the fly                                                                                                                                          
 $ papyri serve                                                                                                                                                                           
 View given function docs in text with ANSI coloring                                                                                                                                      
 $ papyri ascii numpy.linspace                                                                                                                                                            
                                                                                                                                                                                          
╭─ Options ──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ --install-completion        [bash|zsh|fish|powershell|pwsh]  Install completion for the specified shell. [default: None]                                                               │
│ --show-completion           [bash|zsh|fish|powershell|pwsh]  Show completion for the specified shell, to copy it or customize the installation. [default: None]                        │
│ --help                                                       Show this message and exit.                                                                                               │
╰────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯
╭─ Commands ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ ascii                                                                                                                                                                                  │
│ bootstrap                                                                                                                                                                              │
│ browse                                                                                                                                                                                 │
│ build-parser                                                                                                                                                                           │
│ drop                                                                                                                                                                                   │
│ gen                           Generate documentation for a given package.                                                                                                              │
│ ingest                        Given paths to a docbundle folder, ingest it into the known libraries.                                                                                   │
│ install                       WIP, download and install a remote docbundle                                                                                                             │
│ open                                                                                                                                                                                   │
│ pack                                                                                                                                                                                   │
│ relink                        Rescan all the documentation to find potential new crosslinks.                                                                                           │
│ render                                                                                                                                                                                 │
│ serve                                                                                                                                                                                  │
│ serve-static                                                                                                                                                                           │
╰────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯