Adding semantic token support

[chomosuke]

Fixes #156.
Fixes #140.

I wouldn't say I've made semantic tokens look good on every languages out there, but I do think this is good enough to be merged for now and be slowly improved later on. I do also think it is a significant improvement over how semantic tokens currently looks with nvim 0.9.

Here's how rust looks with treesitter only highlighting:

Here's how the same piece of rust looks with semantic token but before this PR, as you can see, it's quite unsightly:

Here's how the same piece of rust looks with semantic token after this PR, notice how the doc test got syntax highlighting as it has been labeled by rust-analyzer:

BTW, I don't think parameters should be red but I can't think of any better color other than white so I'm opened to suggestions.

[jhossbach]

BTW, I don't think parameters should be red but I can't think of any better color other than white so I'm opened to suggestions.

Maybe something like jetbrain's one dark theme?

[chomosuke]

@jhossbach not bad, I'll take that suggestion for now.

[jhossbach]

hey @navarasu, can we get this reviewed&pushed? I would love to use this colorscheme again!

[DoumanAsh]

@chomosuke Just for your information, I noticed string highlighting may not behave well with inline variables (in this example I have variable member_id)

Not sure if it bug in rust-analyzer or neovim cannot handle well variable inside string

[navarasu]

@chomosuke Can you please revert parameter colour change alone as it is not this PR scope? So that I can merge this code

[chomosuke]

@navarasu Done, shall I open param orange in another PR?

[chomosuke]

@DoumanAsh you can use :Inspect to check how are each char labeled. I highly suspect this is rust-analyzer or treesitter not updating or labeling the wrong thing.

[navarasu]

If we are changing the color, we need to check all language. I have handpicked all these color by checking look and feel on multiple languages. Raise it an issue, I will check it