Future Request: Support multiple databases in single project

[Fsher07]

As you know, we can now create more than one database and in my opinion it is very useful. Also firebase itself suggests to use the property to separate prod-staging environments. In FireCMS, it is very easy to do it. We just need to add a database id to useFirestoreDataSource hook. Then, use that parameter as the second input of getFireStore. If it empty, it automatically gets the default database