yarn start - ran your server once - used by run in your VPS/Server host.
yarn dev - ran your server locally with changes.
A telegram bot is just a web server that listens the bot events from telegram and in DEV mode is just a pooling from telegram (not cool for production bots), but in PRD mode its listening the webhook events direct from telegram (thankfully to Telegraf that helps with it).
You'll need to create a bot and get its private key to put in the environment file root .env (just copy the .env.example and remove .example).
All the environment will be changed looking to variable process.NODE_ENV = "prd", then it'll be production or dev it'll be your local server when you ran.
TOKEN_BTC=EXAMPLE_BOTFATHER_TOKEN - your token from botfather
PORT=3000 - just for local purposes.
URL_HEROKU=https://myapp.com/ - Where you deployed/hosted the telegram bot server (not just heroku, can be your vps ip for example the place you listen your port).
- Update telegraf version to 4.
- Upgrade to typescript.