Filter/Block messages by keywords

**Is your feature request related to a problem? Please describe.**
After telegram channels beginning to show ads, It's really annoying that I can also see them in rooms through bridge, especially when they are pushed by Element.

**Describe the solution you'd like**
Add keyword filters in global settings and per room settings, messages containing keywords are not displayed in the room (hidden), and will be displayed again if the keyword is canceled.

**Describe alternatives you've considered**
Element support notifications of messages containing keywords, so it's also acceptable if can just filter notifications by keywords.