Add BorderRadius field to ImageBundle (#14457)

# Objective

- Fixes #14453

## Solution

- Added BorderRadius to ImageBundle

## Testing

- Did you test these changes? If so, how?

- Tested on a random picture I found in the examples and it added a
border radius.

- Are there any parts that need more testing?

- I don't fink so.

- How can other people (reviewers) test your changes? Is there anything
specific they need to know?

- Apply a border radius to a random picture.

crates/bevy_ui/src/node_bundles.rs

@@ -83,6 +83,8 @@ pub struct ImageBundle {
     pub image: UiImage,
     /// The color of the background that will fill the containing node.
     pub background_color: BackgroundColor,
+    /// The border radius of the node
+    pub border_radius: BorderRadius,
     /// The size of the image in pixels
     ///
     /// This component is set automatically