[studio] Add confirmation for closing file with unsaved changes

src/olympic/studio/modlib/include/studio/imguiutil.hpp

@@ -303,6 +303,34 @@ class FilePicker {
 
 };
 
+class QuestionPopup {
+ 	private:
+		enum class Stage {
+			Closed,
+			Opening,
+			Open,
+		};
+		Stage m_stage = Stage::Closed;
+		bool m_open{};
+		ox::String m_title;
+		ox::String m_question;
+
+	public:
+		ox::Signal<ox::Error(ig::PopupResponse)> response;
+
+		QuestionPopup(ox::StringParam title, ox::StringParam question) noexcept;
+
+		void open() noexcept;
+
+		void close() noexcept;
+
+		[[nodiscard]]
+		bool isOpen() const noexcept;
+
+		void draw(StudioContext &ctx, ImVec2 const &sz = {}) noexcept;
+
+};
+
 [[nodiscard]]
 bool mainWinHasFocus() noexcept;