Provide github action to automatically update vcpkg port file on release

[jwillemsen]

---

Is your feature request related to a problem? Please describe.
For projects hosted on github it would be convenient to have a vcpkg action to automatically update the port in vcpkg when there is a new release

Proposed solution
Easy to use vcpkg github action to automatically update the port and create a PR on a release of a project on github

Describe alternatives you've considered
Manually update port file and make a PR

[johnwason]

I have done some partial work on an action like this for a private registry:

https://github.com/robotraconteur/vcpkg-robotraconteur/blob/master/.github/workflows/update_port.yml

https://github.com/robotraconteur/vcpkg-robotraconteur/blob/master/scripts/update_port.py

This does not call vcpkg to update the version database.