More progress on tab-complete

There are missing parts to the "account-based" emotes that needs to be
completed before emote completion can be considered done. For now, when
I've been testing, I've been manually injecting the oauthClient and
oauthToken to the settings file with the `user_subscriptions` scope

src/widgets/mainwindow.hpp

@@ -17,6 +17,7 @@ namespace chatterino {
 
 class ChannelManager;
 class ColorScheme;
+class CompletionManager;
 
 namespace widgets {
 
@@ -25,7 +26,8 @@ class MainWindow : public BaseWidget
     Q_OBJECT
 
 public:
-    explicit MainWindow(ChannelManager &_channelManager, ColorScheme &_colorScheme);
+    explicit MainWindow(ChannelManager &_channelManager, ColorScheme &_colorScheme,
+                        CompletionManager &_completionManager);
     ~MainWindow();
 
     void layoutVisibleChatWidgets(Channel *channel = nullptr);
@@ -48,6 +50,7 @@ private:
 
     ChannelManager &channelManager;
     ColorScheme &colorScheme;
+    CompletionManager &completionManager;
 
     Notebook notebook;
     bool loaded = false;
@@ -144,6 +147,8 @@ private:
     };
 
     pajlada::Settings::Setting<QRectWrapper, QRectWrapper> windowGeometry;
+
+    friend class Notebook;
 };
 
 }  // namespace widgets