Keeping the Azure bicep type templates up to date

This library has a lot of benefits an I can see cases were it could be used within other applications. The concern is about it been kept up to date, and new / updated Azure template items not been available via bicep on day 1 of release and until this is updated. The therefore propose the follow changes to remove this problem.

1. Within the library start up read a boolean config flag (keep updating) if the application wants to check for updates, this is to keep backwards capabilities
2. If the keep updating flag is selected to true, carry out a check to establish if Azure template updates have been published by downloading the overall file, or checking its version against the latest update held within the app.
3. If the versions are out of sync using some of the generate code, via the ARM Swagger API download the updated templates , serialise to the same format of those stored within this library and store in a local side file.
4. If the keep updating flag is set when a call is made to establish the list of items by calling GetIndexedTypes aggregate the templates held within the resource section of the library and those updated items recorded within the update local side file

Additional logic could also be added that when this library does get updated it clears down the load side file

In doing this it will keep this library and Bicep automatically up t date with rest of Azure without having to keep republishing this library.

No files or tests are named. Start by tracing library startup configuration and the GetIndexedTypes entry point, then review how resource templates are stored and how the ARM Swagger API could supply updates. Done would require an agreed design for opt-in updating, local side-file aggregation, version handling, and cleanup after library updates.

Written by the indexing model from the issue text.