Bring CHANGELOG up to date (#1452)

CHANGELOG.md

@@ -1,5 +1,36 @@
 # Changelog
 
+## Unreleased
+
+### Bug fixes
+
+* Replace `in?`, method from ActiveSupport, with `include?` to prevent exception "undefined method `in?`" on non-Rails app. ([#1405])
+
+[#1405]: https://github.com/thoughtbot/shoulda-matchers/pull/1405
+
+### Features
+
+* Add support for Rails 6.1. No new Rails 6.1 features are supported, but only
+  existing features that broke with the upgrade. ([#1418])
+
+* Add support for RVM (Ruby Version Manager) to setting up local environment. ([#1424])
+
+* Add support for alias in matcher define_enum. ([#1419])
+
+* Add support for Ruby 3.0. ([#1406], [#1427])
+
+[#1406]: https://github.com/thoughtbot/shoulda-matchers/pull/1406
+[#1418]: https://github.com/thoughtbot/shoulda-matchers/pull/1418
+[#1419]: https://github.com/thoughtbot/shoulda-matchers/pull/1419
+[#1424]: https://github.com/thoughtbot/shoulda-matchers/pull/1424
+[#1427]: https://github.com/thoughtbot/shoulda-matchers/pull/1427
+
+### Improvements
+
+* Remove deprecated warnings emitted on Rails 6.1 in ActiveModel errors. ([#1444])
+
+[#1444]: https://github.com/thoughtbot/shoulda-matchers/pull/1444
+
 ## 5.0.0.rc1 - 2021-06-04
 
 ### Bug fixes