[vello_encoding] Declare padding in binding types to match WGSL layout

crates/encoding/src/clip.rs

@@ -16,6 +16,7 @@ pub struct ClipBic {
 #[repr(C)]
 pub struct ClipElement {
     pub parent_ix: u32,
+    _padding: [u8; 12],
     pub bbox: [f32; 4],
 }
 

crates/encoding/src/path.rs

@@ -209,6 +209,7 @@ pub struct Path {
     pub bbox: [f32; 4],
     /// Offset (in u32s) to tile rectangle.
     pub tiles: u32,
+    _padding: [u32; 3],
 }
 
 /// Tile object.