Add update checker to launcher (#478)

launcher: add release update checker

Co-authored-by: nmzik <Nmzik@mail.ru>

src/launcher/include/updateChecker.h

@@ -0,0 +1,34 @@
+#ifndef UPDATE_CHECKER_H
+#define UPDATE_CHECKER_H
+
+#include <QNetworkAccessManager>
+#include <QObject>
+
+class QByteArray;
+class QWidget;
+
+class UpdateChecker final: public QObject {
+	Q_OBJECT
+
+public:
+	explicit UpdateChecker(QWidget* parent);
+
+	[[nodiscard]] static bool IsSupported();
+	void Check(bool manual);
+
+signals:
+	void CheckingChanged(bool checking);
+
+private:
+	struct UpdateInfo;
+
+	static UpdateInfo ParseUpdateInfo(const QByteArray& data);
+	void              FetchUpdateInfo(const char* url, bool fallback, bool manual);
+	void              ShowUpdateResult(const UpdateInfo& info, bool manual);
+
+	QWidget*              m_parent           = nullptr;
+	QNetworkAccessManager m_network;
+	bool                  m_checking_updates = false;
+};
+
+#endif // UPDATE_CHECKER_H