Fix docs link in readme (#166)

Author: Manishearth

README.md

@@ -3,7 +3,7 @@ to the [Unicode Standard Annex #29](http://www.unicode.org/reports/tr29/) rules.
 
 [![Build Status](https://github.com/unicode-rs/unicode-segmentation/actions/workflows/rust.yml/badge.svg)](https://github.com/unicode-rs/unicode-segmentation/actions/workflows/rust.yml)
 
-[Documentation](https://unicode-rs.github.io/unicode-segmentation/unicode_segmentation/index.html)
+[Documentation](https://docs.rs/unicode-segmentation)
 
 ```rust
 use unicode_segmentation::UnicodeSegmentation;