[Meta] Add Whitelist

[bbinto]

• https://appbot.co/apps/926238-firefox-focus-the-privacy-browser/reviews/475076741
• http://appbot.co/apps/926238-firefox-focus-the-privacy-browser/reviews/488627651

[bbinto]

Allow some form of whitelisting so that people can disable content blockers selectively for sites where it does not work. Not sure how this fits in Focus though. Which is supposed to be Always On.

It may also be difficult to contain cookies on just a single site. All the WebViews share their caches. Not sure how much control we have.

[sblatz]

mozilla-mobile/focus-android#957

Also be sure to follow all related tickets found in this comment

[oliviabrown9]

Requested by user via https://bugzilla.mozilla.org/show_bug.cgi?id=1523132