Add support for strings on the LHS of function definitions

[MichaelChirico]

Closes #143

[MichaelChirico]

I think the new tests are good & look like they're passing so my edits to tags.scm are WAI? My first time touching tree-sitter so please hand-hold if that's wrong 🙏

I think backticked names were already captured, but adding a test here since that's a useful edge case to keep tabs on.

I wonder if shorthand-lambdas should be included as well, but decided against it as out-of-scope for this PR for now, WDYT?

[MichaelChirico]

Friendly ping! If you're swamped that's fine, just reminding before I forget about it myself :)

[DavisVaughan]

I wonder if shorthand-lambdas should be included as well

This actually would be included because native anonymous functions are part of function_definition

fn <- \(x) x

[DavisVaughan]

I was a little worried about this because capturing (string) captures the " or ' in the name too, and I was wondering how github would work with that.

But I'm remembering that we already capture backticks in the name for something like `fn` and that works fine due to github's good fuzzy search:

So I think just using (string) over (string_content) is fine, and you'll see "my_function" pop up in the github ui, but you'll still be able to nicely match against it with my_ IIUC. If we are wrong, this isn't hard to change in the future.