Provides a slim TextDecoder polyfill for Edge

ui/app/utils/classes/text-decoder.js

@@ -0,0 +1,16 @@
+// This is a very incomplete polyfill for TextDecoder used only
+// by browsers that don't provide one but still provide a ReadableStream
+// interface for fetch.
+
+// A complete polyfill exists if this becomes problematic:
+// https://github.com/inexorabletash/text-encoding
+export default window.TextDecoder ||
+  function() {
+    this.decode = function(value) {
+      let text = '';
+      for (let i = 3; i < value.byteLength; i++) {
+        text += String.fromCharCode(value[i]);
+      }
+      return text;
+    };
+  };