elaborate Deploy and Environment in the README

README.md

@@ -3,12 +3,35 @@
 ## Technical
 The bot is build with framework for telegram bots [grammY](https://grammy.dev) and deployed to [Fly.io](https://fly.io/)
 
+### Environment
+To run the bot you need env BOT_TOKEN defined.
+
+It can be set either in your local `.env` file or fetched from the [dotenv-vault](https://www.dotenv.org/docs/quickstart).
+
+Workflow of working with dotenv-valut is:
+1. you run an app with set env var DOTENV_KEY
+I.e. for bot that would we runing in cli:
+```
+DOTENV_KEY='<environment_key>' ts-node ./src/Bot.ts
+```
+2. DOTENV_KEY defined which environment will be loaded
+3. you can see the actual env vars either in your .env files or by opening the vault with `npx dotenv-vault keys {environment_name}`. So for production it would be
+```
+npx dotenv-vault keys production
+```
+
 ## Deploy
 The bot deployed with GitHub actions.
 
 Basics of using it for Fly.io are here - https://fly.io/docs/app-guides/continuous-deployment-with-github-actions/
 
-Details of it with grammY are here - https://grammy.dev/hosting/fly
+To access `BOT_TOKEN` stored in dotenv-vault pipeline need a `DOTENV_KEY`.
+
+`DOTENV_KEY` is stored as a github [environment secret](https://docs.github.com/en/actions/deployment/targeting-different-environments/using-environments-for-deployment). Therefore to make it work
+1. `DOTENV_KEY` is included to the workflow job as `jobs.<job_id>.environment` (see https://docs.github.com/en/actions/deployment/targeting-different-environments/using-environments-for-deployment#using-an-environment)
+2. `DOTENV_KEY` value is saved as Fly `secret` which will be used in a machinve running the app.
 
-### Environment
-See https://www.dotenv.org/docs/quickstart
+### References
+https://www.dotenv.org/docs/languages/nodejs/github-actions - CI/CD in Node.js with GitHub Actions
+https://fly.io/docs/reference/secrets/ - Fly.io secrets
+https://grammy.dev/hosting/fly - host grammY bot on Fly.io