added return EXIT_SUCCESS in main

oss-internship-2020/sapi_lodepng/README.md

@@ -11,4 +11,5 @@ TODO
 - check if security policy can be stricter
 - ~~use addDirectoryAt instead of addDirectory~~
 - ~~modify tests assertions~~
+- add useful prints to unit tests
 

oss-internship-2020/sapi_lodepng/main.cc

@@ -123,5 +123,5 @@ int main(int argc, char *argv[]) {
   generate_one_step(images_path);
   generate_two_steps(images_path);
 
-  return 0;
+  return EXIT_SUCCESS;
 }