message: add date to changelog for v0.12.0
diff: @@ -6,7 +6,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
  -## [0.12.0]
  +## [0.12.0] - 2020-07-09
  ### Added
  - `diagnosticLevel` option to limit/control the noise in the console diagnostics
  ### Changed
  