add explanation

readme.MD

@@ -1,5 +1,11 @@
-# COVID-19 Telegram updates every day
+# COVID-19 statistics updates at Telegram
 
-Data is hosted in `https://github.com/pomber/covid19`
+## How it works
 
-Integration with [Telegram Action](https://github.com/appleboy/telegram-action)
+It gets data from https://github.com/pomber/covid19, and makes it available in a channel on Telegram via [Telegram Actions](https://github.com/appleboy/telegram-action).
+
+You can enter the [channel for Brazil](http://t.me/covid19brazil) to see the updates.
+
+## Extending
+
+To extend this project for you country you can fork and replace the `TELEGRAM_TO` secret in your repository, using the channel id for it.