Add DeepWiki badge (#1643)

Author: scarroll32

README.md

@@ -2,6 +2,7 @@
 
 [![Build Status](https://github.com/activerecord-hackery/ransack/workflows/test/badge.svg)](https://github.com/activerecord-hackery/ransack/actions)
 [![Gem Version](https://badge.fury.io/rb/ransack.svg)](http://badge.fury.io/rb/ransack)
+[![Ask DeepWiki](https://deepwiki.com/badge.svg)](https://deepwiki.com/activerecord-hackery/ransack)
 [![Code Climate](https://codeclimate.com/github/activerecord-hackery/ransack/badges/gpa.svg)](https://codeclimate.com/github/activerecord-hackery/ransack)
 [![Backers on Open Collective](https://opencollective.com/ransack/backers/badge.svg)](#backers) [![Sponsors on Open Collective](https://opencollective.com/ransack/sponsors/badge.svg)](#sponsors)