return (#984)

when generating a new project, `main.cc` will include a `return 0;` at
the end of the `int main()` function

I think it's generally good practice to do so

Co-authored-by: Jeromos Kovacs <[email protected]>

src/Cmd/New.cc

@@ -32,6 +32,7 @@ static constexpr std::string_view MAIN_CC =
     "#include <iostream>\n\n"
     "int main() {\n"
     "  std::cout << \"Hello, world!\" << std::endl;\n"
+    "  return 0;\n"
     "}\n";
 
 static std::string