[Wasm][Stdlib] Add kotlin.js.JsExport annotation

libraries/stdlib/wasm/src/kotlin/js/annotations.kt

@@ -0,0 +1,16 @@
+/*
+ * 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
+
+/**
+ * Exports top-level declaration on JS platform.
+ *
+ * Can only be applied to top-level functions.
+ */
+@ExperimentalJsExport
+@Retention(AnnotationRetention.BINARY)
+@Target(AnnotationTarget.FUNCTION)
+public actual annotation class JsExport