We should keep our roadmap updated

As a part of the numfocus summit @rgbkrk rightly pointed out that it's a shame we don't keep this repository updated! Is there a reason it isn't currently kept up-to-date? I think it could be useful to do so (and I'm happy to put in time trying to update the projects that I help out with).

Conversely - if we're *not* going to update a lot of this documentation, perhaps we should consider sunsetting some of these? I feel like it almost looks *worse* if we have roadmaps that aren't updated at all (e.g. over the course of 2 years), vs roadmaps that aren't visible.

Thoughts?