credits: Remove support for wide pages, wrap longer lines

It destroyed the layout pretty much and didn't go well with adding new
sections to the right page of the only section using it (Special Thanks).
Still not convinced this is the optimal solution, but why not use the
space if we have it.
Add portfolio website section for artists

Intended for use with audio and graphics artists who can add a link to
our in-game credits this way. The "Special Thanks" section was chosen
because it contains links to other pages already.
Grammar fix