Ability to postprocess, transform or have lifecycle events

[airtonix]

Basically it'd be great to have something that allows us to create transformed copies of single documents or collections.

If there was a set of events for the source and each document within:

makeSource({
  ...
  events: {
    start () {}
    document (document) {}
    collection (collection) {}
    async done () {
      const { brandSettings } = await import('.contentlayer/generated')
      await fs.writeFile('web.manifest',
        JSON.stringify(generateManifest(brandSettings))
      )
    }
  }
})