Update README.md

README.md

@@ -7,6 +7,11 @@ A Radix trie for suggestion search, it allows searching for data indexed by a se
 * Customizable suggestions data, you can add anything associated with a word or a set of words.
 * Non-fuzzy suggestion retrieval in µs to ns for even millions of entries.
 
+## Note
+
+This crate uses a nightly feature #![feature(round_char_boundary)]
+it only works on nightly.
+
 ## Examples  
 
 A common usage for suggestion tries is to find data like words, documents, executables and any other data that is associated with a set of words;
@@ -53,4 +58,4 @@ assert_eq!(results.unwrap()[0].title, "Rat");
 
 ## Docs  
 
-check the docs [here](https://docs.rs/suggestion_trie/latest/suggestion_trie/)
+check the docs [here](https://docs.rs/suggestion_trie/latest/suggestion_trie/)