Add textmate grammar

[anthony-c-martin]

Related to #596
Related to #2098

Preview the highlighting using GitHub Linguist here

[shenglol]

This is awesome!

[majastrz]

secret [](start = 74, length = 6)

I think it'd be worth highlighting limitations of TM in these tests as well. For example it'd be ok if for was treated as a keyword even if it was also the name of the loop item variable. (And equivalent clashes elsewhere in the grammar as well.)

[majastrz]

[majastrz]

This is great!

One question we need to answer at some point is whether we should include the TM grammar in the VSIX. I think it'd be neat to have coloring appear immediately while the server loads, but it makes it harder for users to notice semantic highlights issues. Maybe we shouldn't do that until we have an experience for detecting and easily enabling semantic highlights in config to work around theme issues?

[anthony-c-martin]

This is great!

One question we need to answer at some point is whether we should include the TM grammar in the VSIX. I think it'd be neat to have coloring appear immediately while the server loads, but it makes it harder for users to notice semantic highlights issues. Maybe we shouldn't do that until we have an experience for detecting and easily enabling semantic highlights in config to work around theme issues?

Personally, I'd only want to include it in the VSIX for hovers, and possibly for use in markdown fenced code blocks. I think we'd need to make the TM grammar significantly more robust (inc full error recovery) to provide highlighting before semantic tokens kick in.