feat: Support for `textDocument/semanticTokens`

[angelozerr]

feat: Support for textDocument/semanticTokens

Fixes #238

@FalsePattern, @CppCXY here my current work for semantic tokens support which starts working.

• Use only textDocument/semanticTokens/full
  • Use an implementation of RainbowVisitor. You need to enable semantic tokens (for the moment I don't know how to select by default this checkbox)

• Use SemanticTokensColorsProvider API to get TextAttributesKey from tokenType, tokenModifiers:

   public @Nullable TextAttributesKey getTextAttributesKey(@NotNull String tokenType,
   @NotNull List<String> tokenModifiers,
   @NotNull PsiFile file);

• By default uses DefaultSemanticTokensColorsProvider
• TODO: provide an extension point to use a custom SemanticTokensColorsProvider
• Provide a semantic tokens inspector view to understand what is colorized (I did that because I was totally lost without this inspector):

Please read LSPSupport/md documentation that I'm updating (not finished) to see more information like mappings between semantic token/modifiers and the TextAttributeKey.

[angelozerr]

@FalsePattern @CppCXY I have tested my semantic tokens support with several language servers and the result seems good, but the support must be improved again.

As it is working, do you want me to merge this PR ASAP so you can install a nightly build and you can play with semantic tokens, so you can provide feedback?

If you are OK with this idea, I could merge it ASAP, but please consider that this support is experimental and it requires some improvements.

[CppCXY]

As it is working, do you want I merge this PR ASAP in order to that you can install nighly build and you play with semantic tokens to give is feedback to improve it?

I agree, I will also test this feature ASAP

[angelozerr]

I agree, I will also test this feature ASAP

Ok I will try to merge it today.