Indicate an active filter

Summary

Create some indicator for a filter being active (preferably also indicating what the filter is).

Reasoning

Now that filters have moved into a closable tab, it's not always obvious whether or not you have a filter active. Sometimes this leads to TAs thinking there are no requests, while in reality it's just because they accidentally didn't disable a previously set filter. If the page would display "Only displaying [questions/submissions] for [assignment] of [course] in [room]" or something along those lines.