Update Readme To Make the Features of the Package Explicit. ros2bag2video.py only works with compressed image stream

[hakunaMatataHub]

I am running Master branch with ros2 foxy, and trying to convert a color stream (image_raw) to mp4. Apparently this script only works for compressed images out of the box, you can modify the 'img = self.bridge.compressed_imgmsg_to_cv2(msg, self.msg_fmt)' to ' img = self.bridge.imgmsg_to_cv2(msg, self.msg_fmt)' in listner_callback function in the ros2bag2video.py executable. I further commented out the some code in the _playback_ros_bag function to make it compatible for non-compressed image stream, here is how it looks

 def _playback_ros_bag(self):
        print("Starting ROS bag playback...")
        process = subprocess.Popen(
            [
                "ros2",
                "bag",
                "play",
                self.bag_file,
                # "-r",
                # str(self.rate),
                # "--topics",
                # # HACK AJB Use this for SkateBot
                # # "/camera_node/image_raw/compressed",
                # # HACK AJB Use this for joeys.
                # "/je7c/camera/compressed",
            ]
        )
        return process

    P.S this will work for ros2 image_raw non compressed streams but it breaks the capability to set rate, and topic name by passing arguments to the script from cmd line. For my use case I was cool with the original fps and my bag had only one stream

[cardboardcode]

@hakunaMatataHub May I get your help to provide an example of a ROS 2 bag with compressed images and one without so I can reproduce the issue better?