feat(organize_garage): add new exercise for rust exams

subjects/organize_garage/README.md

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+## organize_garage 
+
+### Instructions
+
+Create a structure `Garage` with generic values. It will have the following public fields:
+- `left` as `Option<T>`.
+- `right` as `Option<T>`.
+
+It will implement the following public methods:
+- `move_to_right`: Moves the values from left to right.
+- `move_to_left`: Moves the values from right to left.
+
+> The generic type will need to have `Add` and `Copy` traits implemented. It will also need to derive `Debug`.
+
+### Usage
+
+Here is a program to test your function.
+
+```rust
+use organize_garage::*;
+
+fn main() {
+    let mut garage = Garage {
+        left: Some(5),
+        right: Some(2),
+    };
+
+    println!("{:?}", garage);
+    garage.move_to_right();
+    println!("{:?}", garage);
+    garage.move_to_left();
+    println!("{:?}", garage);
+}
+```
+
+And its output
+
+```console
+$ cargo run
+Garage { left: Some(5), right: Some(2) }
+Garage { left: None, right: Some(7) }
+Garage { left: Some(7), right: None }
+$
+```