listen to an event in obsidian and clean up the listener onunload

obsidian-events.js

// In this example I'm listening to an event in metadataCache.
class MyPlugin extends Plugin {
  private eventRef: EventRef
  
  async onload(): Promise<void> {
    this.eventRef = this.app.metadataCache.on("changed", (file: Tfile) => doStuff(file))
  }

  onunload(): void {
    this.app.metadataCache.offref(this.eventRef)
  }
}