refactor: add explicit this-> where possible

I have knowingly skipped some files/portions of files where this would
create merge conflicts for other open PRs.

src/providers/twitch/EmoteValue.hpp

@@ -8,17 +8,17 @@ struct EmoteValue {
 public:
     int getSet()
     {
-        return set_;
+        return this->set_;
     }
 
     int getId()
     {
-        return id_;
+        return this->id_;
     }
 
     const QString &getChannelName()
     {
-        return channelName_;
+        return this->channelName_;
     }
 
 private: