[Feature] Support decoding unsigned tokens from firebase emulator

[rromanchuk]

The Admin SDKs use an environment flag

I can take a crack it after I take a look at admin sdk source implementation.

Helpful details firebase/firebase-tools#2764

[rromanchuk]

Actually, it's as easy as JWT.decode(token, nil, false), hard part is designing the less than ideal branching

[fschuindt]

@rromanchuk How about the verification? How that would happen? I'm talking about the verify function implementation.

I'm going to close this for now. Please, anyone, feel free to re-open this. I'm looking forward to more details on how to perform that implementation on the verify function.