WIP: [parsers] Add tree-sitter POC

[forivall]

At the very least, this is waiting on tree-sitter/tree-sitter#481 to be merged and released, so the patch-package hackage can be removed.

Very POC, requesting feedback. As tree-sitter's parsing internals are written in C, this requires some changes to get the WASM binary to load, so feedback on that in particular would be appreciated.

[fkling]

So, am I correctly understanding that this is the JavaScript parser generated by tree sitter?
I see that it supports various languages. Does that mean we could also add a parser for e.g. Bash?

The incremental stuff sounds interesting! Will have to look into that some more at some point.

[forivall]

Exactly, yes, this is the JavaScript parser that tree-sitter generates (from tree-sitter-javascript). I wanted to see what the structure its JavaScript AST looked like and see if it's ESTree or not, and the best way i thought of was to submit it here, then other people can look at how tree-sitter works! And yes, this means we can add parsers for whichever languages tree-sitter can parse.

For the incremental stuff to work fully, it looks like we have to notify the tree-sitter internals about the edits (see the docs and their playground's code, which, like astexplorer, uses codemirror), but getting that to work would take additional changes to astexplorer's redux-saga data model, and i just didn't have time for that then.