Batch Request Documentation

**Is your feature request related to a problem? Please describe.**
It has been an extremely frustrating process to find how to perform batch requests (in fact, I still haven't found how) because documentation around performing batch requests is all out of date (including the page saying that the old form of batch requests will stop working and to refer to client documentation).

Due to rate-limiting and the likes, it would be hugely helpful to be able to batch requests like file updates when moving many files from one folder to another. I'm likely going to have to piece this together as a raw HTTP request instead of an google api method, if that's even possible.

**Describe the solution you'd like**
It would be nice to have clear, concise instructions on batching requests using this library or it should be clearly stated that it's not in the scope of this project. At the moment basically every thread about batching includes information that no longer works or just dies off without resolution.

**Describe alternatives you've considered**
To be able to batch requests I'm likely going to have to perform a direct HTTP request to the API for file updates, or institute a timeout and process requests one-by one. Neither solution is optimal.

**Additional context**
#513
#1130 includes information regarding http2, but no examples of "tight loops" or how this helps batch requests
#121 includes reference to the deprecation of batch endpoints, but once more no concise documentation on how to accomplish this post global endpoint
#740 once more suggests http2 is magically going to fix issues with batching, but suggest "per-api batch methods still exist"
#290 , #338 include ideas/outdated information about batching.