Add recording to opus file

Use the FFmpeg opus muxer to record an opus file.

PR #3978 <https://github.com/Genymobile/scrcpy/pull/3978>

app/src/recorder.c

@@ -66,6 +66,8 @@ sc_recorder_get_format_name(enum sc_record_format format) {
         case SC_RECORD_FORMAT_MKV:
         case SC_RECORD_FORMAT_MKA:
             return "matroska";
+        case SC_RECORD_FORMAT_OPUS:
+            return "opus";
         default:
             return NULL;
     }