Merge pull request #16 from per1234/readme-intro

Add an intro to the readme to explain what the tool does

Author: per1234

README.md

@@ -1,8 +1,19 @@
+# libraries-repository-engine
+
 [![Test Go status](https://github.com/arduino/libraries-repository-engine/actions/workflows/test-go.yml/badge.svg)](https://github.com/arduino/libraries-repository-engine/actions/workflows/test-go.yml)
 [![Check Go status](https://github.com/arduino/libraries-repository-engine/actions/workflows/check-go.yml/badge.svg)](https://github.com/arduino/libraries-repository-engine/actions/workflows/check-go.yml)
 [![Check Prettier Formatting status](https://github.com/arduino/libraries-repository-engine/actions/workflows/check-prettier-formatting-task.yml/badge.svg)](https://github.com/arduino/libraries-repository-engine/actions/workflows/check-prettier-formatting-task.yml)
 [![Spell Check status](https://github.com/arduino/libraries-repository-engine/actions/workflows/spell-check-task.yml/badge.svg)](https://github.com/arduino/libraries-repository-engine/actions/workflows/spell-check-task.yml)
 
+This is the tool that generates [the Arduino Library Manager index](http://downloads.arduino.cc/libraries/library_index.json).
+
+Every hour, the automated Library Manager indexer system runs this tool, which:
+
+1. checks every repository in the [Library Manager list](https://github.com/arduino/library-registry) for new [tags](https://git-scm.com/book/en/v2/Git-Basics-Tagging)
+1. checks whether those tags meet [the requirements for addition to the index](https://github.com/arduino/library-registry/blob/main/FAQ.md#what-are-the-requirements-for-publishing-new-releases-of-libraries-already-in-the-library-manager-list), publishing [logs](https://github.com/arduino/library-registry/blob/main/FAQ.md#can-i-check-on-library-releases-being-added-to-library-manager)
+1. adds entries to the index for compliant tags
+1. pushes the updated index to Arduino's download server
+
 ## BUILD
 
 ```