Add emulator suite support and data for use with the emulator suite for 'test' and 'development' environments

[NathanWEdwards]

The Firebase Emulator Suite package has been included in the project, however, emulator suite initialization and the README description on using the emulator suite with the project is incomplete. Performing testing and development with the emulator suite offers an alternative to accessing remote Firebase instances and is ideal for making temporary changes and when working offline.

Acceptance criterion:

• Firebase entities (i.e. Auth, Firestore, FirebaseStorage) are available in development and test environments with the emulator suite.
• NPM scripts are made available for running the project in development and test environments with the emulator suite when an environment variable is set.
• A data directory for the emulator suite is made available.
• The project README is updated to include instructions for using the emulator suite in development and test environments.

[NathanWEdwards]

Pull request 22 introduces a script to start the Firebase Emulator Suite. Pull request 43 introduces fixes to this script and adds documentation for configuring the Firebase Emulator Suite. The documentation provides details about how to emulate Firebase Services (e.g. Auth, Firebase Storage).

npm run dev will attempt to launch the Firebase Emulator Suite with NextJs dev, if the FIREBASE_EMULATORS_IMPORT_DIRECTORY environment variable is set to an existing directory.