Deprecation of `main` and new versioning system

[Jonathing]

As of today, SharedActions will no longer be updating the main branch unless otherwise necessary. Each new major addition made to SharedActions will now constitute a new version branch, beginning with v0 to indicate testing of the new GitVersion system and subproject versioning framework.

Once branch v1 is made, I will close this issue. This is just to keep track of progress on my end, and for anyone to ask questions if necessary.