Bump prerelease levels instead of prepatch in preview-release GH action (#863)

Author: reese

.github/workflows/preview-release.yaml

@@ -16,7 +16,7 @@ jobs:
         id: bump-semver
         with:
           current_version: ${{ steps.get-latest-tag.outputs.tag }}
-          level: prepatch
+          level: prerelease
       - uses: actions-ecosystem/action-push-tag@v1
         with:
           tag: ${{ steps.bump-semver.outputs.new_version }}