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

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

@@ -0,0 +1,30 @@
+// 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 `() {
+    companion object {
+        val `@invalid val@`: Int = 23
+        fun `invalid fun`(): Int = 42
+    }
+}
+
+// FILE: test.js
+function box() {
+    var InvalidClass = this["export_invalid_name_class"]["invalid@class-name "]
+
+    if (InvalidClass.Companion["@invalid val@"] !== 23)
+        return "false: expect exproted class static variable '@invalid val@' to be 23 but it equals " + InvalidClass.Companion["@invalud val@"]
+
+    var result = InvalidClass.Companion["invalid fun"]()
+
+    if (result !== 42)
+        return "false: expect exproted class static function 'invalid fun' to return 23 but it equals " + result
+
+    return "OK"
+}