Improve Alpine detection

[HugoDF]

Websites using v3 like flutter.dev don't get detected as using Alpine since they're not populating the window.Alpine global.

We could extend the detection functionality by checking if there are elements with x-data attribute that have an initialised Alpine component attached.

[coder2000]

This would be good, as the extension doesn't detect Alpine on my site. I guess that is why, as I don't add it to window.Alpine.

[JeremyJaydan]

I was wondering why it disappeared after I switched to the alpine npm package.

I don't mind manually setting alpine as global, a tip in the readme could be useful though.