✏️ [ FEAT REQ ] Notifications filter

[adamhotep]

I would like to be able to filter notifications by content or sender. (This is a superset of #60.)

Specifically, I'd like to be able to key on things like these:

• Unknown sender (#60)
• Private number (#60)
• Unknown sender AND toll-free number
• Text includes "stop to quit" (case insensitive)
• Text includes "stop to cancel" (case insensitive)
• Toll-free number and text includes "STOP" (case sensitive)

(I'm okay manually defining toll-free numbers. A regex like ^18([0-9])\1[0-9]{7}$ would do it for the US. If it's not a regex, that'll end up being ten entries, so not the end of the world.)