Draft: Add more categories in the storage bar

The "Other files" category in About -> Storage was a bit too vague for me, so I thought to add more detailed categories:

• Documents (~/Documents)
• Downloads (~/Downloads)
• Anbox (~/anbox-data)
• Libertine (~/.cache/libertine-container)

I also included ~/.cache (except libertine-container), ~/.config and ~/.local/share under Used by apps

Adding four colors to the previous palette wasn't trivial so I took this new colors from baobab

I moved the Free space item in the list at the bottom, to reflect the order in the bar