Add warning about not changing class name of vue password toggle

components/settings.vue

@@ -36,7 +36,8 @@
 <style>
   /* Put a min-width on the Show/Hide password toggle button in the Settings
     tab so that it doesn’t jump around due to the differing amount of space
-    taken up by the different labels. */
+    taken up by the different labels. The class name is set by the component
+    and has other styles that act on it so do not change that. */
   button.button.VuePassword__Toggle {
     min-width: 80px;
   }