Improve wording of shortcut hotbar

[Electroid]

Current shortcuts:

B to open a browser, D to open Devtools, S to turn on (experimental) sharing, L to turn on local mode, X to exit

These shortcuts imply a capital letter, but only lowercase letters work. Instead, we should use the lowercase letters, but either color or bold them to make it more prominent.

[b] opens browser, [d] opens debugger, [l] switches to local mode, [x] exits

I also think we should hide [s] since it's experimental.

[petebacondarwin]

Perhaps we should also accept the upper case letters too?

[Electroid]

Perhaps we should also accept the upper case letters too?

Sounds like a good idea, especially if you've accidentally turned on caps-lock.

[petebacondarwin]

Partially resolved by #363