Common t9n bundle for recurring strings

[jcfranco]

Background

As more components add translations, some strings are being duplicated (e.g., Close) and lead to more t9n bundles in the codebase, which could be streamlined.

Additional considerations

• provide guidelines to ensure string bundles are small and contain enough strings (cap on translations per common bundle?)
• compare initial load/render time between approaches
• need to update t9n utils/interface to merge common bundle
• define non-component asset location
• message fetching logic would need to
  • use the same request/promise to avoid multiple fetches of the common bundle when initialized.
  • merge the common and component messages when setting it on the component
  • types should accommodate ☝️as well
• ensure the common bundle strikes a good balance between file size and included props (including browser compression and caching).
  • exploring bundle-splitting after reaching a certain size would be worthwhile
  • using linting rules to keep the common bundle in check
• defining guidelines on when a string is used enough to be moved into the common bundle.
• updating the translations-json.json-generating logic

cc @anveshmekala

Desired Outcome

• less duplicate code to download on the client side
• possibly enable quicker translation support on components (e.g., if a component only needs a few common strings)
• simpler to add/update common t9n messages

[DitwanP]

Anvesh says that a milestone sometime after May would be favorable.

[anveshmekala]

I think it would be better to implement this post Lit migration. Thoughts @jcfranco ?

[jcfranco]

Agreed.