feat(Escaped Identifiers): add ability to use any symbol wrapped in back ticks.

js/js.translator/testData/box/escapedIdentifiers/topLevelExportedClass.kt

@@ -0,0 +1,24 @@
+// IGNORE_BACKEND: JS
+// RUN_PLAIN_BOX_FUNCTION
+// INFER_MAIN_MODULE
+// !LANGUAGE: +JsAllowInvalidCharsIdentifiersEscaping
+
+// MODULE: export_invalid_name_class
+// FILE: lib.kt
+
+@JsExport
+class `invalid@class-name `() {
+    fun foo(): Int = 42
+}
+
+// FILE: test.js
+function box() {
+    var InvalidClass = this["export_invalid_name_class"]["invalid@class-name "]
+    var instance = new InvalidClass()
+    var value = instance.foo()
+
+    if (value !== 42)
+        return "false: expect exproted class function to return 42 but it equals " + value
+
+    return "OK"
+}