add solution links for recently added chapters

src/generics-traits/advanced-traits.md

@@ -275,3 +275,5 @@ fn main() {
     println!("w = {}", w);
 }
 ```
+
+> You can find the solutions [here](https://github.com/sunface/rust-by-practice)(under the solutions path), but only use it when you need it :)

src/generics-traits/const-generics.md

@@ -141,3 +141,5 @@ pub trait IsTrue {}
 
 impl IsTrue for Assert<true> {}
 ```
+
+> You can find the solutions [here](https://github.com/sunface/rust-by-practice)(under the solutions path), but only use it when you need it :)

src/generics-traits/trait-object.md

@@ -225,3 +225,5 @@ fn main() {
     println!("Success!")
 }
 ```
+
+> You can find the solutions [here](https://github.com/sunface/rust-by-practice)(under the solutions path), but only use it when you need it :)

src/generics-traits/traits.md

@@ -466,3 +466,5 @@ fn main() {
     println!("Success!")
 }
 ```
+
+> You can find the solutions [here](https://github.com/sunface/rust-by-practice)(under the solutions path), but only use it when you need it :)