Splaspage: Add highlights. Fix cfp inclusion.

https://github.com/openSUSE/osem/issues/544
https://github.com/openSUSE/osem/issues/545

@hennevogel perhaps some ideas for styling? :)
Yes, that's exactly what I did.
Yes, it would make sense to add some kind of check for a proposal not to be able to have the type 'Keynote'.