add solution links for recently added chapters

src/generics-traits/advanced-traits.md

@@ -274,4 +274,6 @@ fn main() {
     let w = Pretty("hello".to_string());
     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

@@ -140,4 +140,6 @@ pub enum Assert<const CHECK: bool> {}
 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

@@ -224,4 +224,6 @@ 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

@@ -465,4 +465,6 @@ 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 :)