documentUrlPatterns in menus/contextMenus use match patterns.
Not setting documentUrlPatterns would make it appear in about:newtab but then the menu would also appear in other unwanted pages (e.g. moz-extension:, other about:...).
What I am after is to show the context-menu on these pages only:
['http://*/*', 'https://*/*','about:newtab', 'about:blank']
