message: add date to changelog for v0.12.1
diff: @@ -6,7 +6,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
  -## [0.12.1]
  +## [0.12.1] - 2020-07-15
  ### Changed
  - upgraded to [roku-deploy@3.2.2](https://github.com/rokucommunity/roku-deploy/blob/master/CHANGELOG.md#322---2020-07-14)
  ### Fixed
  