Change webpack config to support Heroku hosts (ToolJet#182)

* Change webpack config to support Heroku hosts

* Update app.json for better instructions

* Correction

Author: Navaneeth-pk

app.json

@@ -15,8 +15,12 @@
         "value": "production"
       },
       "TOOLJET_HOST": {
-        "description": "Public URL of ToolJet installtion.",
-        "value": "https://app.tooljet.io"
+        "description": "Public URL of ToolJet installtion. This is usually https://<app-name-in-first-step>.herokuapp.com",
+        "value": "https://<app-name-in-first-step>.herokuapp.com"
+      },
+      "TOOLJET_SERVER_URL": {
+        "description": "URL of ToolJet server installtion. (This is same as the TOOLJET_HOST for Heroku deployments)",
+        "value": "https://<app-name-in-first-step>.herokuapp.com"
       },
       "LOCKBOX_MASTER_KEY": {
         "description": "Key for encrypting datasource credentials.",

frontend/webpack.config.js

@@ -4,7 +4,7 @@ const path = require('path');
 const environment = process.env.NODE_ENV === 'production' ? 'production' : 'development';
 
 const API_URL = {
-  production: 'https://server.tooljet.io',
+  production: process.env.TOOLJET_SERVER_URL,
   development: 'http://localhost:3000'
 };