Storage "upload" method do not save metadata on Android

[Yarikx]

Metadata is not propagated to native code.

https://github.com/fullstackreact/react-native-firestack/blob/master/android/src/main/java/io/fullstack/firestack/FirestackStorage.java#L157
Metadata map is destructured but never used.

[Salakar]

@Yarikx will sort on my branch (which is going to be merged for v3)

[Yarikx]

@Salakar Cool!

[Salakar]

Done, on my branch.

[auser]

Looking forward to merge this -- working on tests

[Salakar]

Closing as fixed on v3 branch.