add global environment variable feature

packages/node_modules/@node-red/nodes/locales/en-US/common/91-global-config.html

@@ -0,0 +1,19 @@
+<!--
+  Copyright JS Foundation and other contributors, http://js.foundation
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+-->
+
+<script type="text/html" data-help-name="global-config">
+    <p>A node for holding global configuration of flows.</p>
+</script>