add en/string.md

Readme.md

@@ -1,6 +1,6 @@
 # Rust By Practice ([中文 Readme](./zh-CN/Readme.md))
 
-- Online Reading: [https://exercise.rs](https://exercise.rs)
+- Online Reading: [https://practice.rs](https://practice.rs)
 
 Greetings Rustaceans and welcome here， if you have the following problems: 
 
@@ -39,7 +39,7 @@ Another limit for rustlings is that you have to download rustlings to local mach
 
 - more topics and exercises，specially for the hard part of Rust，e.g lifetime、smart pointers、threads 、async/.await etc
 - difficulty from easy to hard，it will minimize the gap between learning and using in projects
-- up-to-date, e.g features which added in Rust 1.58 also have the corresponding exercises in `exercise.rs`
-- Both `course.rs` and `exercise.rs` are designed according to the CS courses in college，so quliaty is the most important factor
-
+- up-to-date, e.g features which added in Rust 1.59 also have the corresponding exercises in `practice.rs`
+- Both `course.rs` and `practice.rs` are designed according to the CS courses in college，so quliaty is the most important factor
+- real practices