Add a drawer with the description of our values

This pull request adds a drawer which contains the description of the values we put behind "internet".
I know the tooltips are used a lot on framasoft but imo there is clearly too much text in them here.

This solution does not use javascript so is better for accessibility.

/!\ Warning, the design is really rough, I'm just putting in place the elements as I see them and will then work on the design and polish everything.