add Send impl for SharedRef<BackingStore> (#154)

src/array_buffer.rs

@@ -99,6 +99,8 @@ impl Delete for Allocator {
 #[repr(C)]
 pub struct BackingStore([usize; 6]);
 
+unsafe impl Send for BackingStore {}
+
 impl BackingStore {
   /// Returns a rust u8 slice with a lifetime equal to the lifetime of the BackingStore.
   pub fn data_bytes<'a>(&'a mut self) -> &'a mut [u8] {

src/support.rs

@@ -169,6 +169,8 @@ where
   }
 }
 
+unsafe impl<T> Send for SharedRef<T> where T: Shared + Send {}
+
 impl<T> Deref for SharedRef<T>
 where
   T: Shared,