Add a way to add Custom CodeMirror support for languages

[NullVoxPopuli]

Is your feature request related to a problem?

I would like to add codemirror support for Ember's gjs and gts filetypes.

I already saw similar issues:

• feat: add Svelte language to CodeMirror #212
• feat: add Vue language to CodeMirror #256
• Syntax highlight for *.astro files #357

but saw that an extensible API was not added, but Svelte support is now just built in to tutorial kit.

I already did the work to create codemirror plugins for https://share.glimdown.com/_uXZKpvFRx63MJp7lEhk6A, code here:

• https://github.com/NullVoxPopuli/limber/blob/main/packages/app-support/codemirror/preconfigured/index.ts#L63
  • packages:
    • codemirror-lang-glimmer (hbs)
    • codemirror-lang-glimmer-js (gjs)
    • for gts, I still need to finish making codemirror-lang-glimmer-ts

Describe the solution you'd like.

a way to pass a function or an array of mappings for filetypes -> plugins for codemirror to load

• the syntax plugin
• the array of support plugins (completions, etc)

Describe alternatives you've considered.

I could PR direct support for gjs/gts to tutorial kit

Additional context

<3

[AriPerkkio]

Sounds good!

I didn't really like #212 and #256 as those added language specific features for all users. Some users may not be interested in Svelte at all, but they'll still need to download the dependencies during development. As far as I know, CodeMirror still lazy loads these so clients won't be downloading unnecessary files though.

I'm interested to see what kind of API this would open for end users. We do want to keep configuring TutorialKit as simple as possible - end users should not need to know much about CodeMirror itself.

[NullVoxPopuli]

The only way I've been able to come up with for how to do this (this being, userland, and not doing what svelte and vue did - even though that'd be easiest) involves exposing a runtime JavaScript config file that would have a codemirror.plugins array that folks could throw whatever in to