add: spdlog and basic client code.

3rd/spdlog/details/windows_include.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#ifndef NOMINMAX
+    #define NOMINMAX  // prevent windows redefining min/max
+#endif
+
+#ifndef WIN32_LEAN_AND_MEAN
+    #define WIN32_LEAN_AND_MEAN
+#endif
+
+#include <windows.h>