CHANGELOG.md: add bundle build change

Author: estroz

CHANGELOG.md

@@ -3,11 +3,13 @@
 ### Added
 
 - Added [`run`](./doc/cli/operator-sdk_alpha_run.md) and [`cleanup`](./doc/cli/operator-sdk_alpha_cleanup.md) subcommands (under the `alpha` subcommand) to manage deployment/deletion of operators. These commands currently interact with OLM via an in-cluster registry-server created using an operator's on-disk manifests and managed by `operator-sdk`. ([#2402](https://github.com/operator-framework/operator-sdk/pull/2402))
-- Added [`bundle build`](./doc/cli/operator-sdk_alpha_bundle_build.md) (under the `alpha` subcommand) which builds, and optionally generates metadata for, [operator bundle images](https://github.com/openshift/enhancements/blob/ec2cf96/enhancements/olm/operator-registry.md). ([#2076](https://github.com/operator-framework/operator-sdk/pull/2076))
+- Added [`bundle build`](https://github.com/operator-framework/operator-sdk/blob/4ea8701/doc/cli/operator-sdk_alpha_bundle_build.md) (under the `alpha` subcommand) which builds, and optionally generates metadata for, [operator bundle images](https://github.com/openshift/enhancements/blob/ec2cf96/enhancements/olm/operator-registry.md). ([#2076](https://github.com/operator-framework/operator-sdk/pull/2076))
 
 ### Changed
+
 - Changed error wrapping according to Go version 1.13+ [error handling](https://blog.golang.org/go1.13-errors). ([#2355](https://github.com/operator-framework/operator-sdk/pull/2355))
 - Added retry logic to the cleanup function from the e2e test framework in order to allow it to be achieved in the scenarios where temporary network issues are faced. ([#2277](https://github.com/operator-framework/operator-sdk/pull/2277))
+- Moved `bundle build` from under the `alpha` subcommand to its own top-level [`bundle`](./doc/cli/operator-sdk_bundle.md) subcommand. ([#2438](https://github.com/operator-framework/operator-sdk/pull/2438))
 
 ### Deprecated