[Feature Request] Allow explicitly supplying previous tag

Some projects don't support semver due to platform limitation. Allowing those projects to explicitly provide previous tag in semver format will be helpful. That way these projects can do a dry run to get next semver version and convert it to their previous versioning schemes.

No files or tests are named in the issue. Start by tracing the action's existing tag inputs and dry-run version calculation, then determine how an explicitly supplied previous tag should enter that flow. Done means projects can provide a previous tag in SemVer format and use a dry run to obtain the next SemVer version.

Written by the indexing model from the issue text.