release: 1.21.0 changelog (#940)

* release: 1.21.0 changelog

Signed-off-by: Ben McNicholl <[email protected]>

* add registry data_source

Signed-off-by: Ben McNicholl <[email protected]>

---------

Signed-off-by: Ben McNicholl <[email protected]>

Author: mcncl

CHANGELOG.md

@@ -1,8 +1,9 @@
 # Changelog
 
-## Unreleased
+## [v1.21.0](https://github.com/buildkite/terraform-provider-buildkite/compare/v1.20.0...v1.21.0)
 
 - SUP-3991: Add ImportState to Test Suite Resource [[PR #934](https://github.com/buildkite/terraform-provider-buildkite/pull/934)] @tomowatt
+- add buildkite_registry data resource [[PR #937](https://github.com/buildkite/terraform-provider-buildkite/pull/937)] @scadu
 
 ## [v1.20.0](https://github.com/buildkite/terraform-provider-buildkite/compare/v1.19.0...v1.20.0)