Add an entry in serverconfig.toml for the time between update reminders (#329)

fix #321

include/ChronoWrapper.h

@@ -0,0 +1,8 @@
+#pragma once
+
+#include <chrono>
+#include <string>
+
+namespace ChronoWrapper {
+    std::chrono::high_resolution_clock::duration TimeFromStringWithLiteral(const std::string& time_str);
+}

include/Common.h

@@ -83,6 +83,7 @@ public:
         std::string HTTPServerIP { "127.0.0.1" };
         bool HTTPServerUseSSL { false };
         bool HideUpdateMessages { false };
+        std::string UpdateReminderTime { "30s" };
         [[nodiscard]] bool HasCustomIP() const { return !CustomIP.empty(); }
     };