Create icons for users without an avatar in desktop notifications (#305)

* Add notifications icon for users without an avatar

* Render icon at higher resolution

* Use scale to render at higher resolution

src/util/common.js

@@ -110,3 +110,7 @@ export function getScrollInfo(target) {
   scroll.isScrollable = scroll.height > scroll.viewHeight;
   return scroll;
 }
+
+export function avatarInitials(text) {
+  return [...text][0];
+}