Add opening tab in popup (#3082)

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

src/widgets/splits/SplitContainer.hpp

@@ -202,6 +202,8 @@ public:
 
     void applyFromDescriptor(const NodeDescriptor &rootNode);
 
+    void popup();
+
 protected:
     void paintEvent(QPaintEvent *event) override;