Optimize docker image build

Author: awitwicki

Dockerfile

@@ -1,7 +1,8 @@
 FROM python:buster
 WORKDIR /app
 RUN mkdir data
-COPY . .
+COPY ./requirements.txt .
 RUN pip3 install -r requirements.txt
+COPY . .
 ENTRYPOINT ["python"]
 CMD ["main.py"]