Release on the .org plugin directory

Before we release to the world we should.
- [x] Make sure someone else in HM has code reviewed my dodgy code
- [ ] Create a plugin icon
- [ ] Create a plugin banner
- [ ] Make sure the plugin is setup for translations
- [ ] Add a `readme.txt`
- [x] Add some unit tests

Review the unchecked release checklist, starting with the plugin's existing release metadata and structure; the issue specifically calls for a plugin icon, banner, translation setup, and readme.txt. Done means each unchecked item is completed and the plugin is ready for submission to the .org directory.

由索引模型根据 Issue 内容生成。