Update changelog

Author: pmatseykanets

CHANGELOG.md

@@ -1,10 +1,16 @@
 # Changelog
 
+## [3.1.0](https://github.com/pmatseykanets/laravel-scout-postgres/releases/tag/v3.1.0) - 2018-10-20
+
+### Added
+
+- Added support for `websearch_to_tsquery()` introduced in PostgreSQL 11
+
 ## [3.0.1](https://github.com/pmatseykanets/laravel-scout-postgres/releases/tag/v3.0.1) - 2018-09-02
 
 ### Changed
 
-- Fix composer.json
+- Fix `composer.json`
 
 ## [3.0.0](https://github.com/pmatseykanets/laravel-scout-postgres/releases/tag/v3.0.0) - 2018-09-02