Add polyfills for IE11

Gruntfile.js

@@ -125,6 +125,7 @@ module.exports = function(grunt) {
                 src: [
                     // Ensure editor source files are concatenated in
                     // the right order
+                    "packages/node_modules/@node-red/editor-client/src/js/polyfills.js",
                     "packages/node_modules/@node-red/editor-client/src/js/jquery-addons.js",
                     "packages/node_modules/@node-red/editor-client/src/js/red.js",
                     "packages/node_modules/@node-red/editor-client/src/js/events.js",

packages/node_modules/@node-red/editor-client/src/js/polyfills.js

@@ -0,0 +1,34 @@
+(function() {
+    var isIE11 = !!window.MSInputMethodContext && !!document.documentMode;
+
+    if (isIE11) {
+        // IE11 does not provide classList on SVGElements
+        if (! ("classList" in SVGElement.prototype)) {
+            Object.defineProperty(SVGElement.prototype, 'classList', Object.getOwnPropertyDescriptor(HTMLElement.prototype, 'classList'));
+        }
+
+        // IE11 does not provide children on SVGElements
+        if (! ("children" in SVGElement.prototype)) {
+            Object.defineProperty(SVGElement.prototype, 'children', Object.getOwnPropertyDescriptor(HTMLElement.prototype, 'children'));
+        }
+
+        if (!Array.from) {
+            // JSONata provides an Array.from polyfill that doesn't handle iterables.
+            // So in IE11 we expect Array.from to exist already, it just needs some
+            // changes to support iterables.
+            throw new Error("Missing Array.from base polyfill");
+        }
+        Array._from = Array.from;
+        Array.from = function() {
+            var arrayLike = arguments[0]
+            if (arrayLike.forEach) {
+                var result = [];
+                arrayLike.forEach(function(i) {
+                    result.push(i);
+                })
+                return result;
+            }
+            return Array._from.apply(null,arguments);
+        }
+    }
+})();