Add forks information to the explore pages
### Problem to solve
Add forks information to the explore pages.
### Further details
All repositories get the stars numbers displayed on the [explore page](https://gitlab.com/explore/). Adding the numbers of forks alongside the stars would add useful information for the visitors. A highly starred and forked repo is strong, and combining these information better represent the health of a repo.
Currently, whoever wants to have the forks information without being logged in must follow the repo link and add `/forks`, e.g. [https://gitlab.com/gitlab-org/gitlab-ce/forks](https://gitlab.com/gitlab-org/gitlab-ce/forks). As this information is not private, let's make it more visible.
### Proposal
This feature request include 2 potential developments:
1. Add the forks number alongside the stars number (the `<i class="fa fa-code-fork" aria-hidden="true"></i>` should be used):

1. As for the [Most stars](https://gitlab.com/explore/projects/starred) menu, a similar one entitled "Most forks" could be added:

### What does success look like, and how can we measure that?
Something similar to the images attached above would be a good achievment.
### Links / references
issue