[Suggestion] Add a generic creator-info widget for all campaigns

[shevegen]

Right now I am playing thorough the nameless fellowship saga. What I found interesting is the art - the art seems quite
distinct from other art before. So I want to know who the author is. Actually, the artist - the one who drew the art for that
campaign.

I can search, and find out, but I am a lazy man. I would like to have that information available as a per-scenario setting
for all campaigns, as-is.

Ideally within the game such as "show campaign background information" or some entry like that.

Here, we should list all authors. Perhaps this already exists stored in XML, so this may then only be a new entry
to show the authors. Perhaps also by allowing you to jump to the profile of the author in the forum (but this is
a secondary suggestion; the "make it easy to find out ALL authors" is the primary part of the suggestion here).

If this functionality already exists then perhaps it can be made more prominent. Half of the top menu while playing
wesnoth I never used or looked at in general - only when I had a use case, such as disabling audio that interferes
with background music from youtube ... (I do like in-game effects though.)

[Toranks]

Currently it is what appears when a campaign is finished, the credits

[egallager]

Currently it is what appears when a campaign is finished, the credits

CreditsWML could definitely be improved, though; like, there are a bunch of keys for it that don't actually currently do anything...

[Celtic_Minstrel]

Adding a button to view a campaign's credits without playing through the campaign also doesn't sound like a bad idea.