Better error messages around pip packages

[costrouc]

Closes #497

[trallard]

@costrouc you mentioned "better docs" inclusion and error messages in this PR - but I cannot see any docs updates only the schema and validations update. Is this an oversight?

[trallard]

@costrouc ping here can you please confirm if any docs were updated elsewhere?

[costrouc]

@trallard when a user supplies an invalid pypi package name they were before this PR prompted with:

Invalid pypi package dependency {v}

now

Invalid pypi package dependency "{v}" ensure it follows peps https://peps.python.org/pep-0508/ and https://peps.python.org/pep-0440/'.

This error message will show up on conda-store-ui and the legacy conda-store ui as well when an invalid pypi package is added. I was adding a link to the reference docs and providing a better error message.

No conda-store specific docs were updated.