nvim-python-docstrings

Make Neovim show highlighted markup inside Python docstrings.

This is implemented via a few steps:

1. Add Tree-sitter language injections to capture string literals that are really docstrings.
2. The injected language is a new intermediate pydocstring language that hides any leading indent in the docstring. This is the key step that prevents docstring indentation from ruining the markup, turning it all into code blocks.
3. A second round of language injections turns the non-insignificant-whitespace portions of the pydocstring into Markdown (sorry; it should be un-hardcoded and default to ReST, but I happen to like pdoc).

Dumb mysteries

Memory corruption

If you open :InspectTree in a Python file with multiple docstrings, and then scroll up/down through the node list, you will see the real document cursor jumping and looping all over the document. This is obviously not good. Twice ever, I have seen nvim segfault. I have never seen any suspect behavior while running Tree-sitter tools on this grammar, and the corruption and segfaults were happening before the grammar had a scanner.c, so at this point I assume it's some horrible undebuggable thing on the nvim side of things.

Occasionally does nothing, with no error output

Somewhere between 10%-50% of the time, the same file in the same working dir will not load the injections. Possibly due to memory issues above. I hope.