use rolling major version tag (v1)

[anapsix]

It would be very helpful to create and maintain a rolling major version tag, to be make dependency tools happy.
For example, we're using Mend Renovate to bump various dependencies, including Github Actions action versions. Since ruby/setup-ruby repo does not have a v1 tag (though it does have a v1 branch), the Renovate bot gets confused, and attempts to bump the v1 to v1.143.0. Personally, the v1 branch makes more sense to me, and feels more appropriate for this purpose, while using tags as unchanging pointers to a specific commit.. but in the context of Github Actions, it appears the rolling version tags are acceptable and preferred.

For example:

• actions/checkout@v3
• actions/github-script@v6
• docker/build-push-action@v4

[eregon]

See #55, a tag makes no sense for this.
Whatever relies on this should accept a branch too.