runner: periodically check if there's a new version available on github and offer a visit

src/runner/update_state.h

@@ -0,0 +1,12 @@
+#pragma once
+
+#include <ctime>
+#include <optional>
+
+struct UpdateState
+{
+    std::optional<std::time_t> github_update_last_checked_date;
+
+    static UpdateState load();
+    void save();
+};