Implement getCountFromServer

[hyungtaecf]

It always was needed to read each document to get the count of documents in a collection. That is very expensive.
But I found that a few months ago, Firestore had introduced a feature "getCountFromServer()" that charges one read to get the count of each 1000 documents. And it is implemented for web, node, swift, and Kotlin but I could not find any implementation for Flutter. It is a very useful feature, so could it be implemented, please?

[stact]

Hey @hyungtaecf

Seems to be already implemented

final snapshot = await yourCollection.count().get();
log(snapshot.count) 

[hyungtaecf]

Thank you so much! I just realized I was checking it at outdated dependencies...