FIX(client): Fix PipeWire not being usable in Flatpaks

PipeWire is correctly built and enabled in a Flatpak runtime, but does
not properly intialize because the .so filename of the library is named
slightly differently there.

See also flathub/info.mumble.Mumble#19 (comment)

src/mumble/PipeWire.cpp

@@ -128,7 +128,15 @@ void PipeWireInit::destroy() {
 static PipeWireInit pwi;
 
 PipeWireSystem::PipeWireSystem() : m_ok(false), m_users(0) {
-	const QStringList names{ "libpipewire.so", "libpipewire-0.3.so" };
+	// clang-format off
+	const QStringList names {
+		// Common names used by Linux distributions.
+		"libpipewire.so",
+		"libpipewire-0.3.so",
+		// Name used by the Flatpak FreeDesktop runtime.
+		"libpipewire-0.3.so.0"
+	};
+	// clang-format on
 
 	for (const auto &name : names) {
 		m_lib.setFileName(name);