feat: add version header

src/main.cpp

@@ -1,6 +1,10 @@
+#include <cstdlib>
 #include <iostream>
 
+#include "version.h"
+
 int main(int argc, char **argv) {
-  std::cout << "Hello" << std::endl;
-  return 0;
+  std::cout << "Hello, world! Version " << VERSION << std::endl;
+
+  return EXIT_SUCCESS;
 }