feat(polyfills): use stdlib for js polyfills.

libraries/stdlib/js/src/kotlin/internalAnnotations.kt

@@ -0,0 +1,10 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package kotlin.js
+
+@Retention(AnnotationRetention.BINARY)
+@Target(AnnotationTarget.FUNCTION, AnnotationTarget.PROPERTY)
+internal annotation class JsNativeImplementation(val implementation: String)