Add support for more webmail clients

[M-J-Robbins]

Look at adding support for webmail clients that use <iframe>'s to display email like web.de, gmx, iCloud.

Any other email clients support requests, please add them to this thread

[theotherstevenc]

Just adding a reminder note that came up in our working session to look into potentially using all_frames

"all_frames": true,

https://developer.chrome.com/docs/extensions/mv3/content_scripts/#:~:text=The%20%22all_frames%22%20field%20allows%20the,topmost%20frame%20in%20a%20tab.&text=boolean-,Optional.,the%20top%20frame%20is%20matched