Upgrade Firebase to 9.*.*

[mfix22]

Follow this upgrade guide to upgrade Firebase to version 9: https://firebase.google.com/docs/web/modular-upgrade

[CheRayLiu]

Hi @mfix22 could I get assigned to this? Thanks!

[mfix22]

Hi @mfix22 could I get assigned to this? Thanks!

@CheRayLiu sure, but please don't feel the need to get assigned in order to submit PRs to fix issues. Anyone is allowed to submit a PR, even without assignment.