added username autocompletions with @

src/util/completionmodel.cpp

@@ -92,8 +92,9 @@ void CompletionModel::addString(const QString &str, TaggedString::Type type)
     this->emotes.insert({str + " ", type});
 }
 
-void CompletionModel::addUser(const QString &str)
+void CompletionModel::addUser(const QString &username)
 {
+    auto add = [this](const QString &str) {
         auto ts = this->createUser(str + " ");
         // Always add a space at the end of completions
         std::pair<std::set<TaggedString>::iterator, bool> p = this->emotes.insert(ts);
@@ -109,6 +110,10 @@ void CompletionModel::addUser(const QString &str)
                 p.first->timeAdded = std::chrono::steady_clock::now();
             }
         }
+    };
+
+    add(username);
+    add("@" + username);
 }
 
 void CompletionModel::ClearExpiredStrings()