fix: make supabase.auth.onAuthStateChange work across browser windows

[i-pip]

What kind of change does this PR introduce?

Bug fix: ensure onAuthStateChange works across multiple browser windows

What is the current behavior?

Addresses #2739 - "onAuthStateChange does not catch auth state changes across multiple windows"

What is the new behavior?

[Andarist]

Note that it might not work if a custom localStorage is provided. So I wonder if this shouldn't listen on a separate key and not on the one responsible for storing the token. That way you could still preserve the token in a different type of storage (like cookies) while being able to broadcast the notification using the localStorage "channel"

[kiwicopple]

@Andarist I think for that to work the other storage provider would need to implement some sort of pub/sub functionality?

I can't think of a way that this could work with cookies - do you have some code that you can share which would clarify how it might function?

[kiwicopple]

Thanks for this @i-pip ! I added your code here : #184

Made a new PR so I could tidy it up a bit. If you get a chance would love you to test out that PR and make sure it's good !