[Feature] Improving in-app documentation and help

[ClementTsang]

Checklist

• I've looked through the documentation and existing open issues for this feature/feature request.

Describe the feature request

There's a lot of instances where a question about how to do something simple in bottom can be answered by "look at the docs online" (e.g. a feature exists at all, how to use it, etc.) However, this is, IMO, not a great solution. While it is definitely a good place to put more detailed solutions/answers/things that don't naturally fit (e.g. troubleshooting steps, supported systems, etc.), the in-app documentation/help leaves a lot to be desired.

Some of it can be improved by things like finishing #159, but doing a lookthrough at the ? help menu and cleaning things up in clap/overall can probably help.

It might also help to add a toggleable "bar" a la htop/top that gives useful keybindings.