Add tagging for develop branch

.github/workflows/docker.yml

@@ -23,6 +23,9 @@ jobs:
         if [[ $GITHUB_REF == refs/heads/master ]]; then
           TAGS="${TAGS},${IMAGE}:latest"
         fi
+        if [[ $GITHUB_REF == refs/heads/develop ]]; then
+          TAGS="${TAGS},${IMAGE}:develop"
+        fi
         echo ::set-output name=tags::${TAGS}
     - name: Login in to registry
       uses: docker/login-action@v1