feat: jinja highlighter

[blaggacao]

Issue #, if available:

Description of changes:

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Pull Request Checklist:

• No backwards incompatible changes were made to Ace's public interface which is defined through the main typings file (ace.d.ts) and its references:
  • https://github.com/ajaxorg/ace/blob/master/ace.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-modes.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-extensions.d.ts

[blaggacao]

@akoreman Hey! Could you help me get set up with a suitable review buddy? This is a first draft, but I'm happy and going to dogfood it in (less critical parts of) production.

Anything that comes up during the test phase, will be amended by my own initiative.

It would be nice to have a preliminary review on the patterns and implementation choices as I was mildly confused by the codbase and how to get a handle on it, so I basically did educated guessing and copy pasting and a lot of long iterations.

I'd hope with some expert eyes on it, the low hanging fruits for improvement can be taken already.

[blaggacao]

Note to self: remove. Or better, still: detect variables of for loops or set directives.

But how?