fix(opatIO): added cstdint header

gcc versions 11 and before did not require this header to be manually specified, above that it does. As we move towrds a standardized compiler version I have brought opatIO in line with more modern gcc expectations

src/opatIO/private/opatIO.cpp

@@ -10,6 +10,7 @@
 #include <cmath>
 #include <limits>
 #include <deque>
+#include <cstdint>
 #include "picosha2.h"
 
 // Function to check system endianness

src/opatIO/public/opatIO.h

@@ -8,6 +8,7 @@
 #include <deque>
 #include <map>
 #include <utility>
+#include <cstdint>
 
 /**
  * @brief Structure to hold the header information of an OPAT file.