Allow any username character in user search

app/assets/javascripts/discourse/lib/user-search.js.es6

@@ -91,7 +91,7 @@ export default function userSearch(options) {
 
   return new Ember.RSVP.Promise(function(resolve) {
     // TODO site setting for allowed regex in username
-    if (term.match(/[^a-zA-Z0-9_\.\-]/)) {
+    if (term.match(/[^\w\.\-]/)) {
       resolve([]);
       return;
     }