message: update CHANGELOG.log to v0.9
diff: +## 0.9 (2020/02/28)
  +
  +- Adds `async/await` support.
  +- Keeps the previous synchronous API, enabled by extra feature `blocking`, disabled by default.
  +- Shorten the import path.
  +- Add missing `Show` and `Episode` types.
  +
  ## 0.8 (2020/01/30)
  - Provide more informational error strings for API.
  