Add `Option<Res>::cloned`

## What problem does this solve or what need does it fill?

`Res` does not implement `Clone`, but instead has a custom `clone` method. This does not play well when using an `Option` that you need to clone since `Option::cloned` requires the inner type to implement `Clone`.

## What solution would you like?

It would be nice to have an extension to `Option` that creates a custom `cloned` method that calls the custom `Res::clone` method. Then I could do something like this:

```rust
let slot_transfer_data = mouse_data
.cloned()
.filter(|m| m.location == MouseLocation::Slot)
.and_then(|m| m.inventory_index);
let map_transfer_data = mouse_data
.cloned()
.filter(|m| m.location == MouseLocation::Map)
.and_then(|m| camera.viewport_to_world_2d(camera_transform, m.position));
```

## What alternative(s) have you considered?

Right now my code looks like this:

```rust
let (slot_transfer_data, map_transfer_data) = if let Some(mouse_data) = mouse_data {
let slot_transfer_data = if mouse_data.location == MouseLocation::Slot {
mouse_data
.inventory_index
.zip(dragged_item.data)
.filter(|(dest_index, (dragged_index, _))| dest_index != dragged_index)
} else {
None
};
let map_transfer_data = if mouse_data.location == MouseLocation::Map {
camera
.viewport_to_world_2d(camera_transform, mouse_data.position)
.zip(dragged_item.data)
} else {
None
};
(slot_transfer_data, map_transfer_data)
} else {
(None, None)
};
```

IMO it's pretty messy. It's possible there's a simpler workaround already existing. I am new to Rust, so this is the best I've got.

## Additional context

I think I know just enough Rust to be able to contribute this if y'all think it's worth it. Also this change doesn't appear to be breaking, so that's nice.