* Refactor searchQueryUpdate action
* Use standard message handler style
* Use name "promiseOrResult" for consistency
* Use standard message handler convention for Yomichan message handlers
* Use common message handler invoker
* Move "yomichan" object setup to a separate file
* Update script imports
* Align message handlers
* Rename Yomichan.prepare to Yomichan.ready
* Add new prepare function
* Improve isExtensionUrl