Rename Library to Reference "CosmosDB" Product Name

[Jeremy Peach]

Last year, Microsoft moved the DocumentDB service under the "CosmosDB" service and now refers to it as the "SQL API for CosmosDB". When people search for things like "access cosmosdb from r", they may not find this solution since it's using the old name.

I propose that we rename the package to something like "CosmosdbR" to make it easier for potential users to find it.

Feel free to assign this issue to me if you would like for me to tackle it. I'd be glad to work on it!