Added a million IE11 polyfills...

src/utils/index.js

@@ -72,6 +72,27 @@ export const addPolyfills = () => {
     };
   }
 
+  if (!String.prototype.startsWith) {
+      Object.defineProperty(String.prototype, 'startsWith', {
+          value: function(search, rawPos) {
+              var pos = rawPos > 0 ? rawPos|0 : 0;
+              return this.substring(pos, pos + search.length) === search;
+          }
+      });
+  }
+
+  if (!String.prototype.includes) {
+    String.prototype.includes = function(search, start) {
+      'use strict';
+
+      if (search instanceof RegExp) {
+        throw TypeError('first argument must not be a RegExp');
+      }
+      if (start === undefined) { start = 0; }
+      return this.indexOf(search, start) !== -1;
+    };
+  }
+
   if (!Array.prototype.find) {
     Object.defineProperty(Array.prototype, 'find', {
       value: function(predicate) {
@@ -119,6 +140,36 @@ export const addPolyfills = () => {
 
   }
 
+  if (typeof Object.assign !== 'function') {
+    // Must be writable: true, enumerable: false, configurable: true
+    Object.defineProperty(Object, "assign", {
+      value: function assign(target, varArgs) { // .length of function is 2
+        'use strict';
+        if (target === null || target === undefined) {
+          throw new TypeError('Cannot convert undefined or null to object');
+        }
+
+        var to = Object(target);
+
+        for (var index = 1; index < arguments.length; index++) {
+          var nextSource = arguments[index];
+
+          if (nextSource !== null && nextSource !== undefined) {
+            for (var nextKey in nextSource) {
+              // Avoid bugs when hasOwnProperty is shadowed
+              if (Object.prototype.hasOwnProperty.call(nextSource, nextKey)) {
+                to[nextKey] = nextSource[nextKey];
+              }
+            }
+          }
+        }
+        return to;
+      },
+      writable: true,
+      configurable: true
+    });
+  }
+
 }
 
 /**