chore: mark as prerelease when tagging an RC

Signed-off-by: Donnie Adams <donnie@acorn.io>

Author: thedadams

.github/workflows/dispatch.yaml

@@ -23,3 +23,4 @@ jobs:
           tag: ${{ steps.tag_version.outputs.new_tag }}
           name: Release ${{ steps.tag_version.outputs.new_tag }}
           body: ${{ steps.tag_version.outputs.changelog }}
+          prerelease: ${{ contains(github.ref_name, '-rc') }}