Export allowInterop in dart:_js_annotations

Change-Id: Ib64eefd52fb014e57a78bc229abe159b8023b394
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/161321
Auto-Submit: Harry Terkelsen <[email protected]>
Commit-Queue: Harry Terkelsen <[email protected]>
Commit-Queue: Sigmund Cherem <[email protected]>
Reviewed-by: Sigmund Cherem <[email protected]>

Author: harryterkelsen

sdk/lib/js/_js_annotations.dart

@@ -7,6 +7,8 @@
 // https://github.com/dart-lang/sdk/blob/master/pkg/js/lib/js.dart
 library _js_annotations;
 
+export 'dart:js' show allowInterop, allowInteropCaptureThis;
+
 class JS {
   final String? name;
   const JS([this.name]);