Discuss: Merge Glimmer Syntax VSCode extension into Glint 2

[machty]

When I first started a Volar spike of Glint, I had to copy the glimmer syntax definitions from vsc-ember-syntax in order for Volar to work. I think the specific reason is that vsc-ember-syntax defines the glimmer-ts and glimmer-js language IDs that Volar expects to be present in order to generate VirtualCodes that use/specify those language ideas.

In other words, Volar needs the syntax definitions to be present in the same project/VSCode extension as the Volar-ized LS/TS-Plugin extension.

So, I've actually already merged in the glimmer-ts syntax, but it's a bit of a hack job, so we should use this issue to discuss:

1. Is it OK that I merged the syntax in?
2. Is there a strong compelling reason to keep the syntax extension separate? (and it should be a strong enough reason to push against Volar conventions)
3. Are there tests or niceties from the vsc-ember-syntax extension I should bring over?
4. Do I need to update any files to add authorship / attribution in Glint?