filter out unmaintained repositories

[yegor256]

It's possible to detect which repository is being actively maintained, for example see this study: https://dl.acm.org/doi/abs/10.1145/3239235.3240501 Let's implement such a filtering (or a similar one) inside discover-repositories.rb

See this one too: https://arxiv.org/pdf/2003.04755

[dfarkhutdinova]

@yegor256 I would like to work on this issue if it's possible. thank you!

[yegor256]

@dfarkhutdinova sure, go ahead!