Support autocomplete hints

[LinusU]

ref: https://developer.apple.com/safari/whats-new/

Safari 12 has added support for detecting fields using these hints, hopefully that means that sites will start to use it soon. Would be nice to add support for detecting this, if it's present it should be very reliable.

[perry-mitchell]

This was partially taken care of (for usernames), but could be extended for passwords, emails etc. Great idea!