Add option to render type labels

[Horusiath]

First: Thanks for this plugin! Without it writing Crystal code would be way worse experience.

What I'd like to propose is to enable read-only labels, that would display what kind of types are inferred for things like variables or method parameters and returns. It'd be great to be able to quickly glance over the type signatures without having to manually put cursor over every single one of them. It's one of the more desired features in IDE supporting languages with strong type inference.

Below I'm attaching an examples from Rust VS Code and Ionide (F# extension for VS Code) to illustrate:

[elbywan]

Hey 👋

That is a nifty feature indeed, I'll look into this when I've got some free time (no promises) 👍

[igbanam]

You can get some inspiration from Pyright. I've seen this behaviour while using coc-pyright.