elixir: Add textobjects queries

[baldwindavid]

Release Notes:

• N/A

Adds textobjects queries for Elixir.

These queries were originally pulled directly from the nvim-treesitter-textobjects repo with this textobjects.scm file, but have been heavily edited for Zed.

[ConradIrwin]

@baldwindavid thanks for this!

Unfortunately Zed and nvim work a bit differently (though I was initially trying to build a compatible implementation with either nvim or helix, neither quite worked for our context).

To update the queries, you'll need to remove use of make-range etc. (compare https://github.com/nvim-treesitter/nvim-treesitter-textobjects/blob/master/queries/zig/textobjects.scm with extensions/zig/languages/zig/textobjects.scm for example.

Zed also does not support most of the object types that nvim does; currently it's just function/class/comment, so you can remove most of them

[baldwindavid]

Thanks, @ConradIrwin . Okay, this has been mostly gutted and ready for another look.

The only surprising thing I notice is that visual select around functions (vaf) selects the entire lines rather than just the function which is problematic for inline/anonymous functions. It appears it is that way in other languages too though and at least daf/caf work as expected.