add MM message

.github/workflows/release.yml

@@ -65,3 +65,12 @@ jobs:
         run: |
           export GITHUB_TOKEN=${{ secrets.CHE_BOT_GITHUB_TOKEN }}
           ./make-release.sh --version ${{ github.event.inputs.version}} --trigger-release
+      - name: Create MM message
+        run: |
+          echo "{\"text\":\":building_construction: Che Devfile Registry ${{ github.event.inputs.version }} has been released: https://quay.io/eclipse/che-devfile-registry:${{ github.event.inputs.version }}\"}" > mattermost.json
+      - name: Send MM message
+        uses: mattermost/action-mattermost-notify@master
+        env:
+          MATTERMOST_WEBHOOK_URL: ${{ secrets.MATTERMOST_WEBHOOK_URL }}
+          MATTERMOST_CHANNEL: eclipse-che-releases
+          MATTERMOST_USERNAME: che-bot