Feature: Implement hot reload for engine.importJs

[Haltarys]

I am using this plugin to add some interactivity to my notes. The JS code I write is kind of big, so, to avoid cluttering my note, I write the business logic in a separate JS file that I import using engine.importJs().

However, Obsidian caches the imports made by engine.importJs. Therefore, when re-running the code block, the engine.importJs('path/to/my/script.js') does not actually reload my script.js after I made changes to it. This considerably slows down my development as I have to continually reload Obsidian for the changes to take effect.

This PR implements a hot reload feature to actually load the script every time the code blocks is re-run.

💡 Hot reload is disabled by default, for backwards compatibility and to save memory.

⚠️ It may cause memory shortage if abused (and other bugs with instanceof, I read your comments), but it will considerably improve DX.

(Thank you for your hard work, Moritz Jung!)