Add support for Firestore v12

[leon]

unmet peer firebase@"^9.0.0 || ^10.0.0 || ^11.0.0": found 12.1.0

Needs a peer dep update 🤓

[leon]

@jamesdaniels Would it be possible to update this?

kind regards
Leon

[Timebutt]

Any news here meanwhile? I noticed firebase v12 started dropping fixes I need in my application, but rxfire and @angular/fire are blocking the upgrade. I took a look at upgrading this repository myself, but some decisions have to be made with regards to how to reexport VertexAI (which was renamed), so I'm not sure I'm the right person for the upgrade.