message: added changelog changes for 0.12.3
diff: @@ -5,6 +5,8 @@ The changelog format is based on [Keep a Changelog](https://keepachangelog.com/e
  ## [0.12.3] - 20-Jun-2019
  +**Milestone**: Dragon
  +
  - Fixed null mosaic property in MosaicHttp
  - Added NodeHttp
  - Fixed Uint8 conversions (control char added)
  @@ -134,6 +136,7 @@ The changelog format is based on [Keep a Changelog](https://keepachangelog.com/e
  - Initial code release.
  +[0.12.3]: https://github.com/nemtech/nem2-sdk-typescript-javascript/compare/v0.12.2...v0.12.3
  [0.12.2]: https://github.com/nemtech/nem2-sdk-typescript-javascript/compare/v0.12.1...v0.12.2
  [0.12.1]: https://github.com/nemtech/nem2-sdk-typescript-javascript/compare/v0.12.0...v0.12.1
  [0.12.0]: https://github.com/nemtech/nem2-sdk-typescript-javascript/compare/v0.11.6...v0.12.0
  