Hariku Developer SDK for Hariku 2.12.0

The Hariku Developer SDK for Hariku 2.12.0.

• Hariku 2.12.0: https://github.com/InfiArtt/hariku/releases/tag/v2.12.0
• DEVELOPERS.md and the packager come from hariku-core v2.12.0
  (08d25cc).
• The template and the store guidelines come from hariku-core main
  (08d25cc).

Download Hariku_V2_Developer_SDK.zip below, or press "Use this template" on
https://github.com/InfiArtt/hariku-sdk to start a repository for your own extension.
The template and the examples are under the MIT License.