Added Subscribe option to channel menu

Added the option to visit the subscription page of a channel from chatterino

src/widgets/splits/Split.cpp

@@ -636,6 +636,16 @@ void Split::showViewerList()
     viewerDock->activateWindow();
 }
 
+void Split::openSubPage()
+{
+    ChannelPtr channel = this->getChannel();
+
+    if (auto twitchChannel = dynamic_cast<TwitchChannel *>(channel.get()))
+    {
+        QDesktopServices::openUrl(twitchChannel->subscriptionUrl());
+    }
+}
+
 void Split::copyToClipboard()
 {
     QApplication::clipboard()->setText(this->view_->getSelectedText());