feat: add pypi to conda mapping

[nichmor]

The PyPI - Conda name mapping that maps a PyPI package to it's known Conda counterpart.

This only works for packages that are available on the conda channels that it references.

This is available at https://conda-mapping.prefix.dev/pypi-to-conda-v0/{channel}/{pypi-normalized-name}.json where the channel is the name of the channel and the {pypi-normalized-name} is the normalized name of the package on PyPI.

Example:
for requests we can use https://conda-mapping.prefix.dev/pypi-to-conda-v0/conda-forge/requests.json, which will give you the corresponding json.

The schema will be saved at this location:
https://conda-mapping.prefix.dev/pypi-to-conda-v0/conda-forge/schema/schema.json

[maresb]

Thanks a lot for this @nichmor!

It seems to me like this would be a lot simpler (in my mind at least) as a table instead of a mapping, as per #11 (comment).

So for PyPI→conda-forge requests you have a list of conda-forge archives that contain a PyPI package named requests. And that list can contain some other useful columns.

For the conda-forge→PyPI requests you have the same list but instead filtered to have PyPI packages that are defined by an archive from conda-forge's requests.

This way you only need one schema and it serves both mappings. Also, when you parse published conda-forge packages, you simply need to add rows to the master table. What do you think?