Add VideoRecorder interface and MediaRecorderVideoRecorder for standard videos

cameraview/src/main/java/com/otaliastudios/cameraview/VideoRecorder.java

@@ -32,6 +32,7 @@ abstract class VideoRecorder {
 
     abstract void close();
 
+
     interface VideoResultListener {
         void onVideoResult(@Nullable VideoResult result);
     }