feat: restructure

string.c

@@ -1,7 +1,4 @@
-#include  "include/string.h"
-#include <stdlib.h>
-#include <string.h>
-
+#include  "tstd/string.h"
 
 size_t str_count_occurrences(const char* str, const char c) {
     size_t i = 0;