Make github.io the deploy target for the latest snapshot and latest x.y.z. release plugins

[dbenn]

The release workflow should deploy the result of ant aavso in vstar/plugin to a github.io directory.

This should happen for snapshot and latest stable release (x.y.z, e.g. 2.5.3) such that we have a top-level plugins directory with snapshot and other x.y.z directories under it with .plugins.lst, vstar_plugins and vstar_plugin_libs directories. VStar's plugin preferences URL can then refer to the appropriate subdirectory.

Doing this will avoid the need to put plugin files in an AAVSO HQ server directory as we do now, and make CI/CD more of a reality.

The plug-in manager base URL will need to change accordingly.

[mpyat2]

So, the plugins will be hosted on github.io. For snapshot we need a separate plugin dir, right?

[dbenn]

That's correct. The URL in preferences can be changed at will or driven by version info in the build or a preference button.