feat: Add move_semantics5 exercise. (#746)

* feat: Add move_semantics5 exercise.

* feat: Add option3 exercise

* Address review comments. Fix typos, sentence formatting.

* Remove unwanted newline.

* Address review comments: make comment inline, fix format in print.

exercises/move_semantics/move_semantics5.rs

@@ -0,0 +1,14 @@
+// move_semantics5.rs
+// Make me compile without adding any newlines or removing any of the lines.
+// Execute `rustlings hint move_semantics5` for hints :)
+
+// I AM NOT DONE
+
+fn main() {
+    let mut x = 100;
+    let y = &mut x;
+    let z = &mut *y;
+    *y += 100;
+    *z += 1000;
+    assert_eq!(x, 1200);
+}