Make it possible to disable service worker at runtime

[psrpinto]

By setting enableServiceWorker: false in block attributes.

[ashfame]

@psrpinto Am I right in assuming Chatrix would gracefully fallback without the service worker and still work, just the multiple instances on a page bit won't be handled?

[psrpinto]

Correct, it works fine without the service worker, as long as there is only one instance of hydrogen running for a given session. The only thing the service worker does is to close the session on the "active" instance whenever the same session is opened in another instance.