Add comment für installing gcc

Dockerfile

@@ -33,7 +33,9 @@ RUN pip install --no-cache-dir poetry && \
 
 FROM base
 
+# Install gcc so packages installed durring runtime may be build
 RUN apt-get update && apt-get install -y gcc && gcc --version
+
 RUN useradd -m -s /bin/bash mqtt_io
 USER mqtt_io
 WORKDIR /home/mqtt_io