chore(docker): run the program with --dry-run by default (#22)

Test the script with --dry-run first, we'll then enable it in production
if everything goes as expected.

Dockerfile

@@ -12,4 +12,4 @@ COPY main.py .
 
 RUN pip install -r requirements.txt
 
-CMD ["./main.py", "--help"]
+CMD ["./main.py", "--dry-run"]