Add jump bar/minimap heading for private declarations

Sources/SwiftUIVisualEffects/Demonstration.swift

@@ -31,6 +31,8 @@ public struct SwiftUIVisualEffects_Demonstration: View {
 	}
 }
 
+// MARK: - private extension SwiftUIVisualEffects_Demonstration
+
 private extension SwiftUIVisualEffects_Demonstration {
 	var linearGradient: LinearGradient {
 		LinearGradient(gradient: Gradient(colors: [.blue, .red]), startPoint: .topLeading, endPoint: .bottomTrailing)