Fix tag name in pre-release GitHub action (#16)

Update the pre-release GitHub action to properly populate the tag name variable.

* Add `outputs` section to `create_tag` step to set `tag_name` output.
* Update `create_prerelease` step to use `steps.create_tag.outputs.tag_name` for `tag_name` and `release_name`.

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Author: tsjnsn

.github/workflows/manual-prerelease.yml

@@ -55,6 +55,8 @@ jobs:
           TAG_NAME="prerelease-$(date +'%Y%m%d%H%M%S')"
           git tag $TAG_NAME
           git push origin $TAG_NAME
+        outputs:
+          tag_name: ${{ steps.create_tag.outputs.tag_name }}
 
       - name: Create Prerelease
         id: create_prerelease