`conda pypi convert` should handle remote packages

[jaimergp]

So far it only supports local files and directories, as seen in #111.

@danyeaw suggests:

I would think we would want the convert command to take multiple formats:

1. Package names: requests, numpy, packaging
2. Version specifications: requests>=2.25.0, numpy==1.21.*
3. (Direct) URLs to wheels: https://files.pythonhosted.org/packages/...

[travishathaway]

@jaimergp,

Does this cover use cases like?

conda pypi convert git+https://github.com/my-org/my-package.git

[jaimergp]

I'm hoping there's a package that helps with the pip-style URL identifiers. If that's easy, yes, if not, probably worth implementing separately, since a workaround would be available (clone first, then run locally).