Instead of using one column layout, it's now switched to two column
layout with source on one side and translation on the other side.
One column layout is still used on smaller screens.
* Fixed up max-width
Instead of using relative metric like 90rem, switched over to
pixels. This also decreases the section so my browser won't struggle
as much with it.
* Added proper outline
Instead of using browser's default, I declare blue-ish outline
manually.
* Add borders to elements
Inspired by Sourcehut.
Alexey Yerin