doc: adds comments to the docker file

Author: shbz80

Dockerfile

@@ -27,4 +27,17 @@ RUN pip install awscli
 ENTRYPOINT ["python", "amazon_book_scraper"]
 # the scraper program has two arguments: num_book and num_reviews
 # both gets a default value of 5 and can be overdriven.
-CMD ["5", "5"]
+CMD ["5", "5"]
+
+# example docker run
+# docker run -it -d -rm --name amazon_scraper shbz80/amazon_book_scraper:latest 10 10
+# -it       : interactive 
+# -d        : detached
+# -rm       : remove after completion
+# --name    : name of the container instance (amazon_scraper)
+# [image]   : docker image (shbz80/amazon_book_scraper:latest)
+# arg1, arg2: additional aguments to ENTRYPOINT (10 10)   
+# other useful commands
+# docker container ls   : list all active containers
+# docker container ls -all  : list all containers
+# docker container prune    : remove all stopped containers