Add OpenCV to README and workflow for example video application

Signed-off-by: Jacki <jacki@thejackimonster.de>

.github/workflows/linux.yml

@@ -21,6 +21,7 @@ jobs:
           sudo apt-get -qq update
           sudo apt-get -qq install ninja-build cmake extra-cmake-modules g++
           sudo apt-get -qq install libhidapi-dev libjson-c-dev libudev-dev libusb-1.0-0-dev
+          sudo apt-get -qq libopencv-dev libopencv-core-dev libopencv-videoio-dev
 
       - name: Build framework
         run: |

README.md

@@ -43,6 +43,7 @@ You can build the binary using `cmake` and there are only three dependencies for
  - [libudev](https://github.com/mcatalancid/libudev)
  - [libusb](https://github.com/libusb/libusb)
  - [Fusion](https://github.com/xioTechnologies/Fusion)
+ - [OpenCV](https://github.com/opencv/opencv)
 
 Fusion is a sensor fusion library which is integrated as git submodule. So when you checkout the 
 repository, just update the submodules to get it. The libraries `hidapi` and `json-c` should be