docs(str): moving the actual documentation on the header

- The documentation on the header allow u to see on the files where the
header is inclued

str/ft_substr.c

@@ -6,22 +6,13 @@
 /*   By: rparodi <marvin@42.fr>                     +#+  +:+       +#+        */
 /*                                                +#+#+#+#+#+   +#+           */
 /*   Created: 2023/11/09 13:54:42 by rparodi           #+#    #+#             */
-/*   Updated: 2025/09/01 18:26:29 by rparodi          ###   ########.fr       */
+/*   Updated: 2025/09/05 16:17:50 by rparodi          ###   ########.fr       */
 /*                                                                            */
 /* ************************************************************************** */
 
 #include "str.h"
 #include <stdlib.h>
 
-/**
- * @brief Extracts a substring from a string.
- * 
- * @param s The source string.
- * @param start The starting index of the substring.
- * @param len The maximum length of the substring.
- * 
- * @return A pointer to the substring, or NULL if memory allocation fails.
- */
 char	*ft_substr(char const *s, unsigned int start, size_t len)
 {
 	char	*str;