feat: Select current text with cmd+a

[dubisdev]

cmd+a was working on Windows as it is a native command on Windows (works out of the box).

Now this command should be available in all platforms.

NOTE: There is a lot of work to do to improve Cerebro component. Migrating to newer React versions will allow us to use the event.code instead of event.keyCode that is deprecated and is also less readable than event.code

event.code === "KeyC" // We know is char C
event.keyCode === 67 // We can't know what char it is

fix #628

[ChFlick]

LGTM 🚀
Weird that it doesn't work on mac out of the box, it's also a native command there.