Only show relevant repositories on explore page (#19361)

Only show relevant repositories on explore page (#19361)

Adds a new option to only show relevant repo's on the explore page, for bigger Gitea instances like Codeberg this is a nice option to enable to make the explore page more populated with unique and "high" quality repo's. A note is shown that the results are filtered and have the possibility to see the unfiltered results.

Co-authored-by: vednoc <vednoc@protonmail.com>
Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: 6543 <6543@obermui.de>