Add withUnsafeBytesAsync function

Sources/JavaScriptKit/BasicObjects/JSTypedArray.swift

@@ -88,6 +88,31 @@ public class JSTypedArray<Element>: JSBridgedClass, ExpressibleByArrayLiteral wh
         let result = try body(bufferPtr)
         return result
     }
+
+    /// Calls the given async closure with a pointer to a copy of the underlying bytes of the
+    /// array's storage.
+    ///
+    /// - Note: The pointer passed as an argument to `body` is valid only for the
+    /// lifetime of the closure. Do not escape it from the async closure for later
+    /// use.
+    ///
+    /// - Parameter body: A closure with an `UnsafeBufferPointer` parameter
+    ///   that points to the contiguous storage for the array.
+    ///    If `body` has a return value, that value is also
+    ///   used as the return value for the `withUnsafeBytes(_:)` method. The
+    ///   argument is valid only for the duration of the closure's execution.
+    /// - Returns: The return value, if any, of the `body`async closure parameter.
+    public func withUnsafeBytesAsync<R>(_ body: (UnsafeBufferPointer<Element>) async throws -> R) async rethrows -> R {
+        let bytesLength = lengthInBytes
+        let rawBuffer = malloc(bytesLength)!
+        defer { free(rawBuffer) }
+        _load_typed_array(jsObject.id, rawBuffer.assumingMemoryBound(to: UInt8.self))
+        let length = lengthInBytes / MemoryLayout<Element>.size
+        let boundPtr = rawBuffer.bindMemory(to: Element.self, capacity: length)
+        let bufferPtr = UnsafeBufferPointer<Element>(start: boundPtr, count: length)
+        let result = try await body(bufferPtr)
+        return result
+    }
 }
 
 // MARK: - Int and UInt support