Update the documentation for Dockerfile creation

[ashwathyk-uc]

• Need mention the filename of Dockerfile
• Need to mention that we need to create a docker file using any editor (vi, vim, nano or gedit)
• Need add a link of dockerhub.
• Add a warning that docker pull limit can be reached and what is the alternative.

[safwanebrahim-uc]

@ashwathyk-uc Done in this PR https://github.com/UniCourt/DataEngineering-Workshop1/pull/8/files

[ashwathyk-uc]

Since the suggested changes are made, closing the issue.