Replaces js with js_interop for wasm compliation (#185)

Author: martyfuhry

lib/src/webcrypto/webcrypto.dart

@@ -26,10 +26,10 @@ import 'dart:typed_data';
 import '../impl_interface/impl_interface.dart';
 import '../impl_stub.dart'
     if (dart.library.ffi) '../impl_ffi/impl_ffi.dart'
-    if (dart.library.js) '../impl_js/impl_js.dart' as impl;
+    if (dart.library.js_interop) '../impl_js/impl_js.dart' as impl;
 import '../impl_stub/impl_stub.dart'
     if (dart.library.ffi) '../impl_ffi/impl_ffi.dart'
-    if (dart.library.js) '../impl_js/impl_js.dart' show webCryptImpl;
+    if (dart.library.js_interop) '../impl_js/impl_js.dart' show webCryptImpl;
 
 export '../impl_interface/impl_interface.dart'
     show KeyPair, EllipticCurve, OperationError;