Create an RCL to replace direct access to langnames.json

[PhotoNomad0]

This is to address issue https://github.com/unfoldingWord/tc-create-app/issues/1582

Features of the RCL:

• will have a copy of the langnames.json compiled-in (in case we cannot fetch it over the internet)

• will cache the last fetched copy of langnames.json

• app will be able to over-ride the URL for langnames.json

• it will be flexible enough to be used by all our apps.

• when app requests the latest langnames, the rcl behavior will be:

  • it will attempt to fetch the latest langnames.json from the URL passed by app, or if not given it will fetch using the default URL
  • if that fails it will return the latest cached version from previous fetch.
  • if no previous fetch, it will return a copy of the langnames.json compiled in.

[birchamp]

@PhotoNomad0 will this change fix all of our apps or is it specific to tCC?