Add setting to change color theme

[Jean-BaptisteC]

Discussed in #162

^{Originally posted by Jean-BaptisteC May 11, 2022}
On about_fragment, at the top left

• Add icon more to give access on theme settings
• Add pop-up to select color theme
  
• Option default is System Default

[Jean-BaptisteC]

Menu has been implemented here #188 but logic code to change theme is missing
In this menu we can add item with checkbox to enable black mode (mode for OLED screen to reduce consumption)