Firestore ORM

A wrapper around and extension to the cloud_firestore library for using Firestore in Flutter. Firestore ORM provides the following features:

• Streamlined conversion of Firestore document data to Dart objects using JSON parsers
• Built-in conversion of Firestore data types to the types expected by json_serializable parsers
• In-memory caching model that retains the data from recently-used queries
• Uses DataStream to provide cached data synchronously for a flicker-free UI on load
• Compares fresh data from Firestore with the cache (on a background thread) to prevent unnecessary UI rebuilds