Add #include <cstdint> needed for compilation on recent gcc version

Author: yodatak

library/SteamworksPy.cpp

@@ -21,6 +21,7 @@
 
 #include <iostream>
 #include <string>
+#include <cstdint>
 
 //-----------------------------------------------
 // Definitions
@@ -1517,4 +1518,4 @@ SW_PY void MicroTxn_SetAuthorizationResponseCallback(MicroTxnAuthorizationRespon
         return;
     }
     microtxn.SetAuthorizationResponseCallback(callback);
-}
+}