Start versioning, tagging and releasing `shared-workflows`

[dsotirakis]

We need to start releasing shared-workflows so we can then have automatic updates for repos they use them using tools like dependabot. Recommended versioning is semver, so we are aligned with the rest of the products across Grafana Labs.

[hairyhenderson]

@dsotirakis FYI I've had success with https://github.com/googleapis/release-please-action for this sort of thing - the only catch is commit messages need to follow the conventional commits convention - LMK if you have questions about it!