Add `codemeta.json`

Background: https://codemeta.github.io/

I think codemeta.json is basically ready to supersede the badly documented zenodo.json.

(https://github.com/codemeta/codemeta/issues/213)

To validate it: https://github.com/caltechlibrary/convert_codemeta

Zenodo has support for it in its roadmap: https://github.com/zenodo/zenodo/issues/1504 but we can add it to our repository already.

Good starting point: https://zenodo.org/record/3816771/export/schemaorg_jsonld

Example: https://github.com/adrn/gala/blob/main/codemeta.json

[astrojuanlu]

1. @satyamroy001 calling this 50 % is a bit optimistic in my opinion 😉
2. The way you solve this issue is by doing a pull request, not by leaving comments here.
3. @abdulmoiz37 asked about contributing, so you could have proposed doing it together.
4. @satyamroy001 You asked twice about the details of poliastro, but in my initial commit I wrote everything you need, so I think you didn’t pay enough attention to it.

Please reflect about this feedback and do better.

[astrojuanlu]

Closed in #1172