fix: make footer fluid responsive

Hey @truongleit,

I've created this variant of your branch to demonstrate a more "fluid" approach to the responsiveness. I've removed the .container class completely, which always creates very strict, stuttering layout changes, when the viewport size changes.

It's a question of taste. Not saying one or the other is better. I'll show both versions to @Ollie and @haus tomorrow, and then we can decide, which one we want to use.

This is a more general decision b/c we should apply these principles to the rest of the page, too.