Add difficulty 8, 9 and 10

app.html

@@ -10,7 +10,7 @@
                     <label class="navbar-text" for="difficulty">Block difficulty:</label>
                     <select id="difficulty"
                             ng-model="$root.difficulty"
-                            ng-options="(value + ' (' + $root.difficultyPrefix(value) + ')') for value in [3,4,5,6,7]"
+                            ng-options="(value + ' (' + $root.difficultyPrefix(value) + ')') for value in [3,4,5,6,7,8,9,10]"
                             ng-change="$root.$broadcast('difficulty-change');"
                             class="form-control">
                     </select>