Add hightlight groups for nvim-treesitter

[DerekStride]

What

The neovim project nvim-treesitter/nvim-treesitter ands some additional highlight groups for better syntax highlighting. I've adapted the work done by @nitishvelu in ChristianChiarulli/nvcode-color-schemes.vim#14 to support the treesitter hightlighting and would like to get it merged upstream in the main dracula/vim plugin.

Rust

Left: Highlighting with nvim-treesitter

Right: Existing highlighting

Ruby

Left: Highlighting with nvim-treesitter

Right: Existing highlighting

[dsifford]

Thanks for the PR @DerekStride.

Looks good for the most part. Can you make sure the changes are aligned with the spec?

I added a few comments of things that stuck out at me, but I didn't comb through each group you added.

Once that's done, this should be good to merge.

[DerekStride]

Can you make sure the changes are aligned with the spec?

Thanks for the quick review @dsifford, I dug through the spec and updated the attributes I could reproduce in the latest commit 32fd093.

[dsifford]

See inline suggestions.

It's important to use the builtin highlight groups wherever feasible because if someone were to switch color schemes, all of the linked dracula groups would still remain linked if the new color scheme does not re-link them. This leads to annoying bugs in some cases, particularly for those who tend to change color schemes on the fly a lot.

[dsifford]

Not sure what these are specifically, but headings are purple and bold and inline code delimited with backticks is green.

[dsifford]

LGTM. We can refine from there if needed. Thanks @DerekStride!