Improve download page
This brings back much of the old look and feel of the old installation page.
We also link to https://www.haskell.org/documentation/ in the "Getting started" page and at the end of the ghcup installation script.
This brings back much of the old look and feel of the old installation page.
We also link to https://www.haskell.org/documentation/ in the "Getting started" page and at the end of the ghcup installation script.