RFC: Archived projects should explain in their readme why they were archived

[Albert Astals Cid]

I ended up in https://invent.kde.org/system/xwaylandvideobridge the other day 
and I was wondering "Why was this archived?".

Most of our stuff gets archived because "It's old and no one cares", but that 
means that if someone cares we would not mind unarchiving it.

Some other things (like let's say KF5 only frameworks and possibly this 
xwaylandvideobridge) are archived because better technologies exist.

I think it would be good if from now on we added a small note in the readme 
explaining why the project was archived and if there's possibility of 
unarchiving it.

What do you think

Cheers,
  Albert

P.S: And ideally also for all the ones we have archived but i know that's a 
lot of work, so this only if someone wants to do it.