Add RELEASE_VERSION environment variable to workflow

Author: TylerS1066

.github/workflows/gradle.yaml

@@ -41,6 +41,7 @@ jobs:
       run: ./gradlew publish --parallel
       env:
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        RELEASE_VERSION: ${{ github.event.release.tag_name }}
 
     - name: Stage jar for Actions
       if: ${{ github.event_name != 'release' }}