Highlighting with tree-sitter

[GordianDziwis]

Treesitter does not seem to work with the previews. But would be a good fit, as you are very concerned with speed.

[issue-label-bot[bot]]

Issue-Label Bot is automatically applying the label feature_request to this issue, with a confidence of 0.55. Please mark this comment with :thumbsup: or :thumbsdown: to give our bot feedback!

Links: app homepage, dashboard and code for this bot.

[liuchengxu]

#1019 finally implements this feature after 3 years :P