add shortcuts attached to joystick buttons

[oiseauroch]

🚀 Feature request

📝 Description

add shortcut from home window to common operation. I all my previous feature phones, joystick keys are shortcuts for often used actions. For my current one, its : 

• joystick top : navigate through files
• joystick bottom : contacts
• joystick left : calendar
• joystick right : write new message

📝 Describe the solution you'd like

I would like to be able to use some shortcuts when there is no notification on the screen. For example :

• joystick top : alarm
• joystick bottom : contacts
• joystick left : calendar
• joystick right : write new message

📝 Describe alternatives you've considered

I'm going to propose a PR to do it.

[Lefucjusz]

@oiseauroch Thank you for your suggestion and proposition of the solution! The layout of the buttons will be further discussed with our team, we'll update you when anything changes in this matter.