message: bindings: opencv: update readme.md
diff: ### Overview
  The SDK provides bindings for OpenCV through the helper methods defined in aditof_opencv.h, which provide a way to convert from the `aditof::Frame` data structure to `cv::Mat`.
  +### OpenCV supported version
  +For the dnn example, the minimum opencv version required is `3.4.1`. Other examples will work with older versions.
  +
  #### Directory Structure
  | Directory/File | Description |
  