Glint language server, etc.

[jamescdavis]

This adds three packages:

• packages/language-server - a language server supporting hbs template:
  • typechecking
  • completion
  • hover
  • go-to-definition
• packages/vscode - a Visual Studio Code extension for @glint/language-server
• test-packages/demo-ember-app - an Ember app to demonstrate @glint/language-server

To see the language server in action:

1. make sure you have run yarn and yarn build in the glint repo to build all packages
2. open packages/vscode in VSCode
3. run the extension (F5 or go to Run in the activity bar and press green play button next to Run Extension)
4. in the Extension Development Host, open test-packages/demo-ember-app
5. open app/components/foo.hbs
6. profit

Notes:

• packages/language-server/src/load-typescript.ts was lifted verbatim from packages/cli. We should probably put this somewhere it can be shared.
• packages/language-server/src/transform-manager.ts is based on (but, at this point, pretty different from) packages/cli/transform-manager.ts. There may be some opportunities for factoring out shared bits.
• there is almost certainly some DRYing up and other refactoring that could happen in packages/language-server/src/glint-language-server.ts and packages/language-server/src/transform-manager.ts.
• I'm not 100% convinced the API and encapsulation boundaries I've defined for packages/language-server/src/glint-language-server.ts and packages/language-server/src/transform-manager.ts are where I'd like them to be, but gotta start somewhere!
• I'm not sure packages/language-server/src/glint-language-server.ts is the correct name for this file/class, but names are hard.
• I also have it working in Vim (via ALE) with an ale_linters Vimscript (which will need to be PRed to ALE)
• there are no tests, yet (in progress)

[dfreeman]

Closing this out to avoid confusion. Thanks for laying the foundation here @jamescdavis!