feat: Add traits1.rs and traits2.rs exercises

Rustlings is currently lacking any exercise that teaches
the basic use syntax and implementation of traits. Adding these
two exercises addresses this issue.

exercises/traits/traits1.rs

@@ -0,0 +1,97 @@
+// traits1.rs
+// Time to implement some traits!
+// 
+// Your task is to implement the trait
+// `AppendBar' for the type `String'.
+// 
+// The trait AppendBar has only one function,
+// which appends "Bar" to any object
+// implementing this trait.
+trait AppendBar {
+    fn append_bar(self) -> Self;
+}
+
+impl AppendBar for String {
+    //Add your code here
+
+}
+
+fn main() {
+    let s = String::from("Foo");
+    let s = s.append_bar();
+    println!("s: {}", s);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn is_FooBar() {
+        assert_eq!(String::from("Foo").append_bar(), String::from("FooBar"));
+    }
+
+    #[test]
+    fn is_BarBar() {
+        assert_eq!(
+            String::from("").append_bar().append_bar(),
+            String::from("BarBar")
+        );
+    }
+
+}
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+// A discussion about Traits in Rust can be found below.
+// https://doc.rust-lang.org/1.30.0/book/second-edition/ch10-02-traits.html

exercises/traits/traits2.rs

@@ -0,0 +1,41 @@
+// traits2.rs
+// 
+// Your task is to implement the trait
+// `AppendBar' for a vector of strings.
+// 
+// To implement this trait, consider for
+// a moment what it means to 'append "Bar"'
+// to a vector of strings.
+// 
+// No boiler plate code this time,
+// you can do this! Hints at the bottom.
+
+trait AppendBar {
+    fn append_bar(self) -> Self;
+}
+
+//TODO: Add your code here
+
+
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn is_vec_pop_eq_bar() {
+        let mut foo = vec![String::from("Foo")].append_bar();
+        assert_eq!(foo.pop().unwrap(), String::from("Bar"));
+        assert_eq!(foo.pop().unwrap(), String::from("Foo"));
+    }
+
+}
+
+// Notice how the trait takes ownership of 'self',
+// and returns `Self'. Try mutating the incoming
+// string vector.
+//
+// Vectors provide suitable methods for adding
+// an element at the end. See the documentation
+// at: https://doc.rust-lang.org/std/vec/struct.Vec.html

info.toml

@@ -221,3 +221,13 @@ mode = "test"
 [[exercises]]
 path = "exercises/standard_library_types/iterators4.rs"
 mode = "test"
+
+# TRAITS
+
+[[exercises]]
+path = "exercises/traits/traits1.rs"
+mode = "test"
+
+[[exercises]]
+path = "exercises/traits/traits2.rs"
+mode = "test"