Add matplotlib dep

Author: scotts

.github/workflows/benchmarks.yaml

@@ -37,6 +37,9 @@ jobs:
           python -m pip install --pre torch torchvision torchaudio --index-url https://download.pytorch.org/whl/nightly/cpu
           conda install "ffmpeg=7.0.1" pkg-config -c conda-forge
           ffmpeg -version
+      - name: Install matplotlib
+        run: |
+          python -m pip install matplotlib
       - name: Build and install torchcodec
         run: |
           python -m pip install -e ".[dev]" --no-build-isolation -vvv