fix: reset stream width before printing

without this, the first line of the serialized result becomes too wide

toml/serializer.hpp

@@ -501,7 +501,7 @@ operator<<(std::basic_ostream<charT, traits>& os, const value& v)
     // get status of std::setw().
     const std::size_t w     = os.width();
     const int         fprec = os.precision();
-
+    os.width(0);
     // the root object can't be an inline table. so pass `false`.
     os << visit(serializer(w, fprec, false), v);
     return os;