Add project search filtering by number of forks

Problem to solve

I want to find projects, but I only want to see projects that have a significant number of forks, which indicates activity.

Further details

GitHub has very detailed filtering options that make search and discovery easier than GitLab.

Proposal

Add fork filtering capabilities equivalent to GitHub:

• node.js forks:<200: Find all node.js repositories with less than 200 forks.
• react fork:true: Find all react repositories including forks.
• react fork:only: Find all react repositories that are forks.

Links / references

• https://forum.gitlab.com/t/gitlab-massively-behind-github-in-discoverability/26131
• https://help.github.com/en/articles/searching-for-repositories#search-by-number-of-forks