adding README to the Docker build process

Dockerfile

@@ -32,6 +32,8 @@ RUN pip install "poetry==$POETRY_VERSION"
 
 COPY pyproject.toml /src
 COPY poetry.lock /src
+# it seems poetry won't finish if there's no README.md
+COPY README.md /src
 RUN chown -R mitodl:mitodl /src
 RUN mkdir ${VIRTUAL_ENV} && chown -R mitodl:mitodl ${VIRTUAL_ENV}