Making it use the demo test branch

Dockerfile

@@ -27,6 +27,9 @@ RUN git clone https://github.com/DrewThomasson/ebook2audiobook.git /home/user/eb
 # Set the cloned repository as the base working directory
 WORKDIR /home/user/ebook2audiobook
 
+# Swap to the demo branch
+RUN git checkout demo
+
 #Install Python dependences from the ebook2audiobook repo
 RUN pip install --no-cache-dir --upgrade -r requirements.txt