docs: fixed regex for parsing base64String, and updated subscribeToPush function. (#73940)
### What?
Change 1:
At line 107, the regex code is now fixed to replace all "-" with "+",
which wasn't as expected with previous code, window.atob() would throw
an error saying the string is not encoded properly. The variable base64
will now have a URL safe base64String.
Change 2:
At line 177 and 178, the function is now updated to call the server
action subscribeUser() with a serialized object instead of a
PushSubscription object, as server actions can only be called with
serialized objects.
### Why?
I followed to docs to setup a PWA project with next, and I encountered
issues with the code mentioned in the documentation.
### How?
The fixed code snippets will work as expected, and anyone following the
docs later can find them helpful.
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Co-authored-by: Lee Robinson <me@leerob.io>
Co-authored-by: JJ Kasper <jj@jjsweb.site>