Use Gradle Wrapper in publishing workflow

See #356

Author: fsteeg

.github/workflows/publish.yml

@@ -10,7 +10,7 @@ jobs:
         with:
           java-version: 1.8
       - name: Publish package
-        run: gradle publish
+        run: ./gradlew publish
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}