Update ci.yml

Add another artefact, with only the plantuml.jar 
See:
https://github.com/plantuml/plantuml/discussions/653#discussioncomment-1631002

.github/workflows/ci.yml

@@ -110,6 +110,16 @@ jobs:
           name: ${{ github.run_number }}-jars
           path: target/*.jar
 
+      - name: Upload jar artifact (only simple jar - without javadoc or sources)
+        if: ${{ matrix.release_from_this_build }}
+        uses: actions/upload-artifact@v2
+        with:
+          name: plantuml-jar
+          path: |
+            target/*.jar
+            !target/*-javadoc.jar
+            !target/*-sources.jar
+
   release:
     needs: [ workflow_config, build ]
     if: needs.workflow_config.outputs.do_release == 'true'