Issue title: Implement Password Autofill for iOS11
 Issue body: https://developer.apple.com/videos/play/wwdc2017/206/

@lime124 @bbinto so iOS11 has an autofill option for things stored in iCloud - this could be an easy win for quick access. @bkmunar is going to investigate if this is possible in Focus and provide estimate for the dev work here but maybe we can sneak this into 4.0?
 Comments: 
 Comment 0: "The next thing to know is that UITextView and UITextField are automatically eligible for consideration or Password AutoFill. So, if you're using these standard controls out of UIKit, you're already in a really good place.

However, if you're rolling your own text fields, no need to worry.

If your text field conforms to UITextInput, it's also eligible for Password Autofill."

I think this makes Password Autofill implementations with WKWebView impossible as it seems to be only designated to the text field classes; which makes sense if they want to make autofill a private API for Safari iOS. @boek 
 Comment 1: Thanks @bkmunar looks like this isn't an option :/ . 
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