Browser Dark Mode (Chrome and Firefox)
       ------------------------------------------------------------------------
       
       Dark Mode luckily has become a thing also in the non-unix world. Finally
       browser can be used with dark interfaces and websites can have
       alternative color schemes.
       
       However, in other operating systems, there is a global toggle for dark
       mode, which also switches the browser into it. This is not the case on 
       linux and unix systems.
       
       Chrome
       ======
       
       Chrome and Chromium starting with version 73 can be tought to start in 
       dark mode:
       
           $ chrome --enable-features=WebUIDarkMode --force-dark-mode
       
       Then go to chrome://settings/?search=themes and switch the theme to 
       "Classic".
       
       Firefox
       =======
       
       Firefox got the dark mode in release 70.
       
           0. Go to "about:config"
           1. Enter "ui.systemUsesDarkTheme" into the search bar
           2. Click "Number" and then "+"
           3. Enter "1" and click the check mark
       
       Right click on a free spot in the icon bar and select "customize". At 
       the bottom left of the screen, you can switch to a dark theme.
       
       Note: If you've set privacy.resistFingerprinting to "true" the CSS dark 
       mode switching won't work. Kudus to @andinus@tilde.zone for figuring 
       this out.
       
       There you go, both browsers are in dark mode now. The UI should be dark
       and also websites that support the @media (prefers-color-scheme: dark)
       directive should make use of it.
       
       You can test it on my webpage (https://codevoid.de). The light version
       has a light gray background and a blue font. The dark version has a dark
       gray background and an orange font.
       
       # Changelog:
       # * 2020-05-17: Created