Extend web UI to make active filters noticeable

[simonkrauter]

• Gitea version (or commit ref): 1.5.1
• Git version: not relevant
• Operating system: not relevant
• Database (use [x]): not relevant
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (any issue list)

Description

The web UI should show somehow, that filters (Label, Milestone, etc.) are active.
Possible ideas:

• Add button to clear all filters like on GitHub (see attached screenshot)
• Give the drop down menu buttons of active filters a different look.

Related: #1893

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs during the next 2 weeks. Thank you for your contributions.

[stale]

This issue has been automatically closed because of inactivity. You can re-open it if needed.