BUG Enables downloads for sdist

[thomasjpfan]

Fixes #35

[thomasjpfan]

@ogrisel In the near feature we are going to have travis build ARM, which means we will still need to use a temporary location to store the wheels.

At this point, I am thinking of using https://github.blog/changelog/2020-07-06-github-actions-manual-triggers-with-workflow_dispatch/ to have a button we can push to "download wheels/sdist from anaconda and upload the to pypi".

[ogrisel]

Thanks @thomasjpfan ! Indeed it would be great to have a workflow trigger to fetch all artifacts and release to pypi.