Update README.md with useful information

README.md

@@ -1 +1,23 @@
 # Simple Test API
+
+## Main Goal
+Useful in code tests:
+- main uri reveals `/api/` uri
+- `/api` returns random http status code
+- for tests, `/api/418` returns 418 http status code
+- if http status code is between `100` and `399` returns image uri
+- if http status code is `5xx` randomly drops connection
+
+## Requirements
+- `node` and `npm` 
+- `.env` for local running
+  - `PORT=3000` or other as you wish
+  - `API_KEY` from [Pexels API](https://www.pexels.com/api/) - to get random image URI
+- for remote hosting I'm using [Heroku](https://dashboard.heroku.com/)
+
+## How to use locally
+- `npm install` 
+- set `.env` variables
+- `node index.js`
+- open `http://localhost:3000` (replace `3000` with your `.env PORT` config)
+