Add source file

Author: fisker

.gitignore

@@ -7,4 +7,4 @@ node_modules
 .pnp.*
 .nyc_output
 # Bundled
-index.js
+/index.js

source/index.js

@@ -0,0 +1,5 @@
+import identifierRegexp from "./regexp.js";
+
+const isEs5IdentifierName = (id) => identifierRegexp.test(id);
+
+export default isEs5IdentifierName;