:tada: Add editing navigation using alt & escape

[MathisFederico]

Adds:

• Navigation can be trigger from inside editors using alt+arrow
• Editing mode can be entered from navigation using alt
• Selection & Focus can be cleared using escape

[FabienRoger]

This looks very good! Pressing alt when exiting a block moves the cursor to the menu bar, making it impossible to move between blocks with the arrows without pressing alt (except if you press alt again to make the cursor exit the menu bar). It might be better to always prevent the alt key moving the cursor to the menu bar? What do you think?

I was not able to fix this, the app style would need to be modified, but I found no easy way of doing it.

[MathisFederico]

Pressing alt when exiting a block moves the cursor to the menu bar, making it impossible to move between blocks with the arrows without pressing alt.

I changed the key to enter/backspace as we can't seem to be able to override the alt button behavior.

[FabienRoger]

I changed the key to enter/backspace as we can't seem to be able to override the alt button behavior.

I like this new shortcut, it makes it natural that it isn't possible to focus out of a block. I don't have a natural idea for a shortcut working both ways...

(I fixed that the user couldn't make new lines by pressing enter inside the block by disabling the shortcut inside blocks.)