Add scala syntax highlights

[dwat3r]

Hi!

I really like helix, so I'd like to add scala syntax highlight and LSP support for it.
Amazingly, LSP support with metals works out-of-the-box, although additional metals commands like import build and others obviously needs to be added.

I've copied the tree-sitter highlights and injections from nvim-treesitter, but found a couple of issues with it, and couldn't figure out it yet, so the syntax highlighting is partial currently. I'm happy to receive suggestions how to migrate the whole from nvim.

[amousset]

I checked open PR before starting #1279 and it happened to be the day another identical PR is opened 😄

To make syntax highlighting work I had to update the tree-sitter-scala submodule.

[dwat3r]

I checked open PR before starting #1279 and it happened to be the day another identical PR is opened smile

To make syntax highlighting work I had to update the tree-sitter-scala submodule.
Thanks, this was also required to make scala syntax highlight work :)

I've corrected the syntax, but I'm not sure why helix doesn't color things like objects and other stuff like neovim with the nvim-treesitter.

Here's a comparison screenshot (both are using their own onedark theme (hx: builtin, nvim: ful1e5/onedark.nvim)):
With neovim treesitter:

helix with this PR:

Also apologies for spoiling some old advent of code for you :D

[archseer]

It's probably the theme definitions not being defined for every syntax scope. I actually prefer it this way because it strikes a nice balance (is it really necessary to highlight every word? Not a single word in the first image isn't highlighted..)

I'll do some debugging locally though.

[dwat3r]

You're right, too much highlight is not very good. Although I've missed the functions being highlighted, but your fix made it perfect! :)

I personally think what is really bad in the neovim theme is the use of italics. It almost looks like a different font, and is distracting.

EDIT:
I've noticed indents were not working, so I've quickly copied what nvim-treesitter has in it's folds.scm, and it works most of the time, on multi-line parameters it indents too much, but otherwise it's much better than nothing.