Add ffmpeg

.github/workflows/ci.yml

@@ -28,6 +28,9 @@ jobs:
         with:
           python-version: ${{ matrix.python }}
 
+      - name: Install ffmpeg
+        run: sudo apt-get update && sudo apt-get install -y ffmpeg
+
       - name: Install dependencies
         run: pip install -r requirements.txt pytest scikit-image moviepy