feat(from_into) : add test for checking unnecessary trailing value

exercises/conversions/from_into.rs

@@ -115,4 +115,18 @@ mod tests {
         assert_eq!(p.name, "John");
         assert_eq!(p.age, 30);
     }
+
+    #[test]
+    fn test_trailing_comma() {
+        let p: Person = Person::from("Mike,32,");
+        assert_eq!(p.name, "John");
+        assert_eq!(p.age, 30);
+    }
+
+    #[test]
+    fn test_trailing_comma_and_some_string() {
+        let p: Person = Person::from("Mike,32,man");
+        assert_eq!(p.name, "John");
+        assert_eq!(p.age, 30);
+    }
 }