Add a command to toggle debugging

[jtpio]

For now debugging is enabled and disabled by clicking on the toggle button:

However this button doesn't correspond to a command for now, but it could.

It would then be possible to map the toggle action to a keyboard shortcut too.

[jtpio]

This looks like this could be done at the same time as #393

[KrzysztofSikoraCodete]

Do we have some list of keyboard shortcut? I didn't find which key will be right.

[jtpio]

We could think about the keyboard shortcuts as a second step?

(since there isn't any for the debugger for now)

[Sandy4321]

can you add more keyboard shortcuts for example run all cells?