Add: Favicon link in the head part of the HTML file

I change the Favicon png file to another one with transparent
background. I also remove the blue background color of the body and the
useless <p> tag.
Change: set the Favicon link with an internet link

The Favicon image is on a server to allow the website to display it.
Avoid using "file:///" because we don't have any server running on some
machine. In the final version, we'll have to change it to the local
Favicon file.