Explain the Element window / visual items

**Is your feature request related to a problem? Please describe.**
People ask me if their messages are encrypted and if so, what they have to look out for. https://element.io/help has entries regarding encryption but doesn't show the badges and what they mean, e.g. that a green shield means "encrypted and verified".

**Describe the solution you'd like**
It would be nice if there could be an overview of all the visual elements of Element, which shows what badges look like for encryption and room settings (e.g. notifications). It'd also be nice if there would be an explanation what the differences between the icons are.

**Describe alternatives you've considered**
The interface of Element itself already shows hints when you hover over the icons. This doesn't show all possible modes though, only the currently active one.

**Additional context**
Signal shows the parts of their application as screenshots in their help, e.g. [for sending messages](https://support.signal.org/hc/en-us/articles/360007060212-Send-a-message).

Whatsapp also has YouTube videos in their help section which show how to do things, e.g. [replying to messages](https://faq.whatsapp.com/general/chats/how-to-reply-to-a-message/).

Maybe since Element is rather suited for "semi-pro users" and you want to establish hydrogen as your "easy" messenger, you might want to explain it there, too?