Add documentation for cosmos db provider transactional batches
Adds documentation for the usage of TransactionalBatch in the Cosmos DB provider when saving changes. See: https://github.com/dotnet/efcore/issues/17308 and https://github.com/dotnet/efcore/pull/36693
Should probably only be merged once 11.0 is out? I could not find a 11.0 or release branching strategy in the repo and the contributing guide said to target main (I only found live)
@roji You're right! Sorry about that, should have probably at-least kept it as draft until the other PR was merged. Will do that now. I had some time left over so didn't mind working ahead a bit and making changes later if needed. Thank you for reviewing despite that!