Tweaked the openSUSE build service links

This adds links to the openSUSE wiki with further information
* https://en.opensuse.org/OpenRA
* https://en.opensuse.org/Games

and avoids linking the download page twice. Also it may be confusing that you don't get a package, but another HTML site with instructions. I tried to mitigate that by renaming the button a bit.
I guess openSUSE users will probably know what they have to do.