Create index.js as entry point for the package

Add main entry point for the package with export options.

index.js

@@ -0,0 +1,8 @@
+// This is the main entry point of the package
+// Directly exports your plugin from sigpro.js
+
+// If your sigpro.js already exports the plugin as default, you can do:
+export { default } from './sigpro.js';
+
+// Or if you prefer CommonJS:
+// module.exports = require('./sigpro.js');