Add release count to project homepage

Problem to solve

Releases are an important part of GitLab projects, but they aren't mentioned anywhere on a project's home page.

Proposal

Add a release count to the project's main page:

Further details

Potentially only show the release count if the project has at least one release.

Also, it might be worth considering dropping the "Tags" count, since these indicators serve similar purposes.

For comparison, GitHub displays a release count on their repo pages: