fix: Add iframe type attibute
fix: Add iframe type attibute

*** SECURITY FIX ***

https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XUL/iframe#a-browser.type
https://developer.mozilla.org/en-US/docs/Displaying_web_content_in_an_extension_without_security_issues

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