Keyboard shortcuts

[murilopolese]

It uses Q for opening the port selection dialog, W for reset, E for stop, R for run and S to save.

The implementation is a 3 step process:

• Create electron shortcuts here and send messages to the web context https://github.com/arduino/lab-micropython-editor/blob/feature/shortcuts/index.js#L139-L162
• Expose this communication to the electron main through the context bridge https://github.com/arduino/lab-micropython-editor/blob/feature/shortcuts/preload.js#L130-L136
• Call the app events when events come from the main context: https://github.com/arduino/lab-micropython-editor/blob/feature/shortcuts/ui/arduino/store.js#L677-L697

Pending issues:

• Since we are using R for run, the item on the app menu "window > reload" is overwritten but it is still displayed. This can be confusing.

[murilopolese]

In conversation with @ubidefeo I think this PR raises the following important question: "what shortcuts should be available to all possible micropython UI?"

Because the electron layer should be ignorant of what UI is being displayed. This is at the very core of the design.
So the editor will have some shortcuts, the possible other UI or wrapper/hosts (go, web, etc...) will have other shortcuts.