Welcome screen

[Zac0511]

I was thinking that a welcome screen for new users would be useful, so that new users can know how to manage their files, use apps from the store

Examples :

• The welcome screen could explain how to manage files
• How to change settings (when the settings app will be out)
• How to use apps from the store
• How to add multiples accounts
• And other things

[KernelDeimos]

@jelveh would it be appropriate to add the good first issue label to this?

[jelveh]

@Zac0511 I'm going to close this in favor of the other more detailed issue you created a few days ago (#588)