chore: release v0.12.0 (#103) (#104)

Author: RafilxTenfen

CHANGELOG.md

@@ -37,6 +37,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ## Unreleased
 
+## v0.12.0
+
 ### Improvements
 
 * [#83](https://github.com/babylonlabs-io/covenant-emulator/pull/83) covenant-signer: remove go.mod