Release 5.0.2 including latest Firebase SDK compatibility updates

[eacardenase]

Commit bd254cb added support for Firebase SDK versions <13, but the latest published release (5.0.1) still restrict the SDK to <12.

Using master directly works just fine, but it would be helpful to publish a new patch or minor release that includes this update.

Thanks in advance, and please let me know if I can help with anything to get this out.