Add gjs/gts support

[NullVoxPopuli]

Adds https://github.com/NullVoxPopuli/rollup-plugin-glimmer-template-tag
However
adding rollup-plugin-glimmer-template-tag as a devDependency then requires

• adding ember-source
  • fine, handled by Use built in types from ember-source instead of the types-packages #118 )
    • except that for monorepos, we can't support yarn@v1
      • unless we allow this all to be blocked by the --typescript app blueprint using the built-in types, semi-related: WIP: Fix --typescript flag by bringing in the blueprint, and removing ember-cli-typescript ember-cli/ember-cli#10216
        (the problem is that the @types/ember* packages and the built in types aren't perfectly compatible)
    • adding ember-source, in turn, requires consumers install @glimmer/component (I think for types), and webpack. for libraries webpack is unreasonable (and unused), but @glimmer/component, is 🤷 a good number of v2 addons will need it anyway (and is added here) For webpack, we'll want to add a pnpm.peerDependencyRules.ignoreMissing entry
• adding ember-template-imports
  • not fine, but Extract preprocessor and babel plugin into their own packages ember-cli/ember-template-imports#143 will help resolve
    • waiting on @achambers & co to publish
    • then waiting on me to update rollup-plugin-glimmer-template-tag to use the new stuff

To Test

1. checkout locally
2. cd $elsewhere
3. npx ember-cli@latest addon gjs-addon -b $addonBlueprint/ --skip-npm --skip-git --addon-only
4. cd gjs-addon
5. pnpm i
6. pnpm build

[NullVoxPopuli]

Note to self: https://github.com/embroider-build/addon-blueprint/pull/108/files#diff-3683017e81620bed14c63b6bbf8dae66d213607772b8b577a6ab6c0c524a507b

.prettierrc config will need updating

[NullVoxPopuli]

gonna close this.

Potential gjs support in @embroider/addon-dev embroider-build/embroider#1518
will change the exact details for adding gjs/gts support