feat(firestore): Added multiple firestore database support

[KSokhal]

#718 Added support for multiple Firestore databases within a single app

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[dr-nyt]

Any ETA on when this will be pushed? Urgently need this feature.

[DracarysBZH]

Hello @lahirumaramba, is there any news on this PR or is there another way to do it that have been implemented already ? Thanks 🙂