show appropriate icon next to amount numbers (and some docs)

README.md

@@ -59,6 +59,10 @@ Under the "Your Identity" screen, click "Advanced", click "Switch Identity / No
 
 For your own web-push tests, change the 'vapid' URL in App.vue, and install apps on the same domain.
 
+### Icons
+
+To add an icon, add to main.ts and reference with `fa` element and `icon` attribute with the hyphenated name.
+
 ### Manual walk-through
 
 - Clear the browser cache for localhost for a new user.