Firestore adapter?

[bzd2000]

Hi,
for a small project a wrote a google firestore adapter,
It covers my use case , so i didn't implement (or investigate) all operaties or query possibilities that it should support (like the mongo adapters do natively)

By design Firestore is already limited in its query possibilities, so it will never support everything.
For example there is no server side count, server side text search etc

If you are interested I can make PR for this adapter.