Push Ionic2 to heroku : Cannot get / - heroku

Question

I'm trying to push my ionic2 project (as a web-app) to Heroku, the deploy is ok, but when I'm accessing to the app, I have a blank page with a "Cannot GET /".
I have an express server, a correct Procfile, but I think the www/ is not build on deploy. Effectively, if I include my www/ folder in my push, the web-app run... (But i don't want versionning my www/ folder).
Here, my package.json. What i'm doing wrong ? Thank you !
{
"name": "ionic-hello-world",
"author": "Ionic Framework",
"homepage": "http://ionicframework.com/",
"private": true,
"main": "server.js",
"scripts": {
"clean": "ionic-app-scripts clean",
"build": "ionic-app-scripts build",
"ionic:build": "ionic-app-scripts build",
"ionic:serve": "ionic-app-scripts serve",
"start": "node server.js"
},
"dependencies": {
"#angular/common": "2.2.1",
"#angular/compiler": "2.2.1",
"#angular/compiler-cli": "2.2.1",
"#angular/core": "2.2.1",
"#angular/forms": "2.2.1",
"#angular/http": "2.2.1",
"#angular/platform-browser": "2.2.1",
"#angular/platform-browser-dynamic": "2.2.1",
"#angular/platform-server": "2.2.1",
"#ionic/storage": "1.1.6",
"angular2-jwt": "^0.1.27",
"auth0-lock": "^10.7.3",
"express": "^4.14.1",
"ionic-angular": "2.0.0-rc.4",
"ionic-native": "2.2.11",
"ionicons": "3.0.0",
"rxjs": "5.0.0-beta.12",
"zone.js": "0.6.26"
},
"devDependencies": {
"#ionic/app-scripts": "^1.0.0",
"typescript": "2.0.9",
"sw-toolbox": "3.4.0"
},
"cordovaPlugins": [
"cordova-plugin-whitelist",
"cordova-plugin-statusbar",
"cordova-plugin-console",
"cordova-plugin-device",
"cordova-plugin-splashscreen",
"ionic-plugin-keyboard"
],
"cordovaPlatforms": [],
"description": "deals: An Ionic project"
}