actually i didn't change the webpack.config.js file.This is how the resolve object looks(there are two resolve objects)
resolve: {
extensions: ['.ts', '.js', '.json'],
modules: [path.resolve('node_modules')]
},
Thanks @xtremeplus and @Axalon ,I have followed all the step mentioned but gsap module is not avaliable . gsap files are there in node_modules and typings folder but its definations are not shown when i import then.???