Include images and saved meshes when pasting Frame

`tiny_skia::Frame` was ignoring images in `Frame::paste`, making images
not show up when created in a `with_clip` context.

`wgpu::Frame` similarly did not pass through meshes in its paste method,
that may have been saved from a nested `with_clip` call.

tiny_skia/src/geometry.rs

@@ -256,6 +256,7 @@ impl geometry::frame::Backend for Frame {
     fn paste(&mut self, frame: Self) {
         self.primitives.extend(frame.primitives);
         self.text.extend(frame.text);
+        self.images.extend(frame.images);
     }
 
     fn translate(&mut self, translation: Vector) {