Twitch API: v5 to Helix migration (#1560)

There's a document in src/providers/twitch/api which describes how we interact with the Twitch API.
Keeping this up to date might be a healthy way for us to ensure we keep using the right APIs for the right job.

src/controllers/notifications/NotificationController.hpp

@@ -43,6 +43,7 @@ private:
     void removeFakeChannel(const QString channelName);
     void getFakeTwitchChannelLiveStatus(const QString &channelName);
 
+    // fakeTwitchChannels is a list of streams who are live that we have already sent out a notification for
     std::vector<QString> fakeTwitchChannels;
     QTimer *liveStatusTimer_;