Add dockerfile and update readme

[Aryllen]

• Add dockerfile.
• Update readme with info about the repo and how to use the dockerfile or image.

Please let me know if this is clear, @kelshmo and @avanlinden.

[avanlinden]

I tested this and was able to successfully build the docker image locally and run the template generation script. Very clear instructions -- thank you for this!

[Aryllen]

Thank you for checking it out and making suggestions, @avanlinden!