Update README.md

Co-authored-by: Steven G. Johnson <[email protected]>

README.md

@@ -112,7 +112,7 @@ printf("%d\n", a);
 ### Casefold
 
 ```c
-// Convert `ß` to its casefold variant `ss`
+// Convert "ß"  (U+00DF) to its casefold variant "ss"
 utf8proc_uint8_t str[] = "ß";
 utf8proc_uint8_t *fold_str;
 utf8proc_map(str, 0, &fold_str, UTF8PROC_NULLTERM | UTF8PROC_CASEFOLD);