Adding Heroku deploy button to Bolt Python starter template

Procfile

@@ -0,0 +1 @@
+worker: python app.py

README.md

@@ -24,6 +24,16 @@ export SLACK_BOT_TOKEN=<your-bot-token>
 export SLACK_APP_TOKEN=<your-app-token>
 ```
 
+## Heroku Deployment
+Use the `Deploy to Heroku` button below to launch this app on Heroku. Ensure your Heroku config vars include the required Slack env variables.
+<!--
+  NOTE: This Deploy to Heroku button currently points to my personal fork
+  to allow testing of the latest changes.
+  Before merging this PR, be sure to update the URL to point to the
+  official Slack bolt-python-starter-template repository (https://github.com/slack-samples/bolt-python-starter-template).
+-->
+[![Deploy](https://www.herokucdn.com/deploy/button.svg)](https://www.heroku.com/deploy?template=https://github.com/allhaile/bolt-python-starter-template)
+
 ### Setup Your Local Project
 ```zsh
 # Clone this project onto your machine

app.json

@@ -0,0 +1,23 @@
+{
+  "name": "Bolt for Python Starter App (Socket Mode)",
+  "description": "A Slack app using Bolt for Python with Socket Mode",
+  "env": {
+    "SLACK_BOT_TOKEN": {
+      "description": "Your bot token (starts with xoxb-)",
+      "required": true
+    },
+    "SLACK_APP_TOKEN": {
+      "description": "Your app-level token (starts with xapp-)",
+      "required": true
+    }
+  },
+  "scripts": {
+    "postdeploy": "echo 'Your Bolt for Python Socket Mode app was deployed!'"
+  },
+  "addons": [],
+  "buildpacks": [
+    {
+      "url": "heroku/python"
+    }
+  ]
+}