Support recording to MKV

Implement recording to Matroska files.

The format to use is determined by the option -F/--record-format if set,
or by the file extension (".mp4" or ".mkv").

app/src/scrcpy.h

@@ -2,11 +2,13 @@
 #define SCRCPY_H
 
 #include <SDL2/SDL_stdinc.h>
+#include <recorder.h>
 
 struct scrcpy_options {
     const char *serial;
     const char *crop;
     const char *record_filename;
+    enum recorder_format record_format;
     Uint16 port;
     Uint16 max_size;
     Uint32 bit_rate;