Add automation for publishing to PyPI

[NeonDaniel]

This automates alpha versioning and publication to PyPI. A dev workflow would look like:

• create branch from dev
• make changes and open a PR to dev (probably not messing with osm_versions.py, though it is possible
• on PR merge to dev, version is incremented by a1
• when ready for release, create a PR that only changes version in osm_versions.py to desired version
• on merge into dev, version spec PR won't increment the version
• Release a non-alpha (this could be added to run on PR merge dev -> master, or on manual creation of release, etc)

[codecov[bot]]

Codecov Report

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[NeonDaniel]

Note that this requires a PyPI token as a secret: https://github.com/OpenVoiceOS/ovos_skill_manager/pull/87/files#diff-a6a80b7ff8485f6d57b2a582f5862616a2388885e3d4e9aaebdd826ff9b7f023R39

For Neon, I added this as an org secret and then restricted the repositories that have access to it to make sure only repos that have valid workflows can use it (a templated or transferred new plugin needs to be granted permission explicitly). This means only org admins can add packages and org write permissioned users can't publish a package under the org's name