ci: test opusenc in CI

.github/workflows/ci.yml

@@ -23,7 +23,7 @@ jobs:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
-        sudo apt update && sudo apt install -y ffmpeg
+        sudo apt update && sudo apt install -y ffmpeg opus-tools
         python3 -m pip install --upgrade pip
         pip install tox tox-gh-actions
     - name: Test with tox