:sparkles: Allow geolocation from the iframe
:sparkles: Allow geolocation from the iframe

As of Firefox v74, in order to use certain web APIs from inside an iframe the appropriate feature policy must be specified via an `allow` attribute.

See:
- https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Releases/74
- https://developer.mozilla.org/en-US/docs/Web/HTTP/Feature_Policy
- https://developer.mozilla.org/en-US/docs/Web/HTML/Element/iframe#Attributes

> "Feature Policy is now enabled by default! Use the <iframe> element's allow attribute (and the HTMLIFrameElement property allow) to set permissions for your frames (bug 1617219)."
> -- https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Releases/74

MethodGrab/firefox-custom-new-tab-page,MethodGrab/firefox-custom-new-tab-page