ci: Add matplotlib dependency

Author: jorisv

.github/workflows/ubuntu.yml

@@ -83,6 +83,7 @@ jobs:
                                    libmimalloc-dev \
                                    python3-numpy \
                                    python3-pytest \
+                                   python3-matplotlib \
                                    robotpkg-example-robot-data \
                                    robotpkg-py${PYTHON3_VERSION}-example-robot-data \
                                    robotpkg-py${PYTHON3_VERSION}-eigenpy \
@@ -108,6 +109,7 @@ jobs:
                                    catch2 \
                                    python3-numpy \
                                    python3-pytest \
+                                   python3-matplotlib \
                                    robotpkg-example-robot-data \
                                    robotpkg-py${PYTHON3_VERSION}-example-robot-data \
                                    robotpkg-py${PYTHON3_VERSION}-eigenpy \