Add an option to automatically switch to darkmode if it's enabled in the device

[sandoche]

A feature idea:

• Automatically activate the darkmode if the device is

Resources: https://stackoverflow.com/questions/50840168/how-to-detect-if-the-os-is-in-dark-mode-in-browsers

[ozzy-simpson]

Here's some Webkit information on this: https://webkit.org/blog/8840/dark-mode-support-in-webkit/

[sandoche]

It's now implemented in the version 1.4.0