Color mentions to match the mentioned users color (#2284)

You can disable this by unchecking "Color @usernames" under `Settings -> General -> Advanced (misc.)`

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

src/common/ChannelChatters.hpp

@@ -18,12 +18,15 @@ public:
     void addJoinedUser(const QString &user);
     void addPartedUser(const QString &user);
     void setChatters(UsernameSet &&set);
+    const QColor getUserColor(const QString &user);
+    void setUserColor(const QString &user, const QColor &color);
 
 private:
     Channel &channel_;
 
     // maps 2 char prefix to set of names
     UniqueAccess<UsernameSet> chatters_;
+    UniqueAccess<std::map<QString, QColor>> chatterColors_;
 
     // combines multiple joins/parts into one message
     UniqueAccess<QStringList> joinedUsers_;