feat: add random wallpaper

[noahfraiture]

Pull Request

Description

This choose a random wallpaper from the selected theme at login.
The thing is that I'm still on the old configuration system so I tried to adapt it to the new without being able to test. It would be good if someone can test. Else, I will make a full restart in a few days with new configuration system.

You could also don't like the idea, I would be glad to hear what you think. I assume that everyone will modify the configuration files to match its need at some point.

Type of change

Please put an x in the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update (non-breaking change; modified files are limited to the documentations)
• Technical debt (a code change that does not fix a bug or add a feature but makes something clearer for devs)
• Other (provide details below)

Checklist

Please put an x in the boxes that apply:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• I have added necessary comments/documentation to my code.

[dieBakterie]

We shouldn't add an launch option for this or comment out by default. It's better to opt in then to opt out.

[noahfraiture]

We shouldn't add an launch option for this or comment out by default. It's better to opt in then to opt out.

I think it's normal to have default option that can be removed. Like the keybinds offer lot of functionnality and most user remove some of them. It's better to have more than less