Add "pin" action to usercards and reply threads (#4692)

src/widgets/DraggablePopup.hpp

@@ -34,6 +34,10 @@ protected:
     // lifetimeHack_ is used to check that the window hasn't been destroyed yet
     std::shared_ptr<bool> lifetimeHack_;
 
+    // Toggles pin status updates action on focus loss, isPinned_ and the pin
+    // button pixmap
+    void togglePinned();
+
 private:
     // isMoving_ is set to true if the user is holding the left mouse button down and has moved the mouse a small amount away from the original click point (startPosDrag_)
     bool isMoving_ = false;
@@ -47,6 +51,9 @@ private:
 
     // dragTimer_ is called ~60 times per second once the user has initiated dragging
     QTimer dragTimer_;
+
+    Button *pinButton_ = nullptr;
+    bool isPinned_ = false;
 };
 
 }  // namespace chatterino