Add a README to the milli crate

milli/README.md

@@ -0,0 +1,16 @@
+<p align="center">
+  <img alt="the milli logo" src="../assets/milli-logo.svg">
+</p>
+
+<p align="center">a concurrent indexer combined with fast and relevant search algorithms</p>
+
+## Introduction
+
+This crate contains the internal engine used by [Meilisearch].
+
+It contains a library that can manage one and only one index. Meilisearch
+manages the multi-index itself. Milli is unable to store updates in a store:
+it is the job of something else above and this is why it is only able
+to process one update at a time.
+
+[Meilisearch]: https://github.com/meilisearch/meilisearch