Jekyll doc example

[mwestphal]

trafficstars

[CharlesGueunet]

Ideas:

• [x] Add a menu / summary
• [x] Add a changelog entry with the changelog of the last relase
• [x] Add an icone in the tab of the browser
• [x] Use the space aside from the big f3d icon at the top

[Meakk]

Comments on the website:

• The link "F3D on github" on the top right isn't great. Can you maybe add a github logo and a better text like "Explore code source on GitHub"
• The /fɛd/ text does not appear correctly on my mobile
• Can we replace the animated gif on the home page with a video?
• For the cpp examples, we should add #include <f3d/xxx.h>