feat: added ft_putstr

srcs/ft_putstr.c

@@ -0,0 +1,12 @@
+#include "libft.h"
+#include <unistd.h>
+
+int ft_putstr(const char *s)
+{
+    int len = 0;
+    if (!s)
+        return write(1, "(null)", 6);
+    while (s[len])
+        write(1, &s[len++], 1);
+    return len;
+}