Improve highlights

[uncenter]

Brings over the improvements made downstream: nvim-treesitter/nvim-treesitter#6619.

[the-mikedavis]

I'd like to keep the highlights query in this repo simple so that it can be used with tree-sitter-cli's highlight command (which only uses this set of captures by default: https://github.com/tree-sitter/tree-sitter/blob/2c064039c7f790c47c1fefe32a85bee756e957ac/cli/src/highlight.rs#L161-L186).

Instead we could add some comments to the top of this file linking to neovim's and others' queries

[uncenter]

Can it not be used if any captures are unknown? I would assume tree-sitter highlight would ignore those captures but still work?

[the-mikedavis]

Unknown captures won't cause an error, they just won't highlight the text at all. So diff.plus and diff.minus for example won't cause any highlighting

[uncenter]

Gotcha.