Additional Firebase Setup in Documentation

[JosephSemrai]

Is your feature request related to a problem? Please describe.
Related to starting the project as a contributor. There are a few errors that contributors may encounter that could be solved with a piece in the contributor documentation.

Describe the solution you'd like
Contributors may encounter issues with oAuth as they first have to enable the respective authentication methods within Firebase. Instructions on this would be appreciated in the contributor guide.

Additionally, there are custom rules (or a default template) that have to be applied to the Firebase database, or else the user encounters this error:

and the app gets stuck on a task

With this, mentioning the process in the documentation for setting up the database and providing the following rules:

{
    "rules": {    
        ".read": true,
        ".write": true
    }
}

may prove to be helpful for new contributors.