Closest real implementation

[Ughuuu]

This is the closest implemention I found that is almost drop in over the real one, maybe needs a layer on top of it to match the API of firebase, and from what I find messages that go from callback are all sent togheter, maybe needs an id parameter to always be sent so that you can differentiate between messages.

I'm taking a look to see if it's doable as I have a game that would just love to port on web and works with firebase. I'll let you know of progress and ask for help if needed and if you want I can create a PR after with changes.

[Ughuuu]

Oh my, just checked and it seems it would be really difficult to do, unsure if impossible, but it seems that unity webgl and tasks don't go along very well.

I was looking however at https://github.com/Cysharp/UniTask to see if I could change this from task as it seems to be a unity task implementation single threaded for webgl.