Make the text of nav/choice buttons unselectable

src/components/ChoiceButton.vue

@@ -53,6 +53,7 @@ export default class ChoiceButton extends Vue {
   border-style: outset;
   outline: none;
   padding: 4pt;
+  user-select: none;
 }
 
 .choice-button:focus {

src/components/NavButton.vue

@@ -53,6 +53,7 @@ export default class NavButton extends Vue {
   width: 100%;
   height: 100%;
   z-index: 1;
+  user-select: none;
 }
 
 .nav-button:hover {