Usage on RSD

[egpbos]

Issue #48 was never really solved, just worked around by adding a link to the discussion.

There are three parts to this.

1. Historical usage: in Show external usage on RSD #48 lists were compiled with template users that could be found through GitHub searches. We should actually add these to the RSD. I've started this today. All mentioned repos in Show external usage on RSD #48 that have a (working) DOI have already been added. I'm looking at whether we want to add the rest as webpages, but the amount of manual work is a bit daunting.
2. Future: with @lyashevska and @abelsiqueira we've been thinking about other ways to track usage. When we start using Copier (soon, see Migration from cookiecutter to copier template #399), we should investigate for instance whether it makes sense to make the template an actual (dev) dependency of the package created. That way, GitHub will automatically track dependents. If people have ideas about this, give a shout!
3. Current usage: if you know of packages that are not yet mentioned on the RSD page, please let me know so I can add it!