Add better descriptions for images at Docker Hub
Unlike PyPI, it seems like there's not a way to tell Docker Hub to infer the description from the contents of the upload. We can probably use the API if we wish to programmatically. But, in any case, we will first need to save the description somewhere in this repo. Then, we can think about how to improve the process of keeping it in sync.
The description should tell users the following things:
- What's contained in the image
- Who's the target audience
- Meaning of tags, and which tag should an user pick and why
- How to use the image
- Links to source code, docs, website etc.
I think https://hub.docker.com/_/python/ is a good example for this purpose.