Add UI to report disreputable sites

[bsclifton]

Carried over from brave/browser-laptop#1370

Need way to block ads found, report scam sites

Blocking un-blocked ads is addressed with #94

Users should be able to report disreputable sites (phishing, scam, etc). Basically, things that should trigger Safe Browsing. It would be ideal if the sites are reported in a way that Safe Browsing could make use of them

[rossmoody]

Pointing this functionality as a consideration to the update in #1149

[fmarier]

Firefox has this functionality:

which takes you to this form.

If we want to do this, we might be able to get Google for a Brave-branded form, or we could use the Google-branded form.