[TASK] Update client lists

[xxxserxxx]

Several OpenSubsonic API servers list clients that can be used with them. I keep noticing that they all miss stmps, even if they include stmp. So I've been going around adding stmps when I notice it. This ticket is just a heads-up.

• On the Navidrome client list (b/c @spezifisch uses Navidrome)
• On the Arch Subsonic page (b/c stmps is in AUR)

I did an announcement on Lemmy for good measure.