Update Git Extensions website

[Mikilll94]

Feature description

Git Extensions website is completely outdated, it shows the 2.x version and it lacks any documentation.

https://gitextensions.github.io/

Maybe it's time to rebuild this website from scratch?

BTW on this website, there are links to Git Extensions tutorials on YouTube which are presented on Windows Vista and Internet Explorer 🤣 🤣 🤣 🤣 🤣

[RussKie]

If you would like to help, we'll happily accept it :)