Improve prefetcher

[johanjanssens]

• [ ] Use a webworker for fetch() instead of handling the request on idle to avoid blocking main thread
• [ ] Implement support for transclusion and substitution of html
• [ ] Default config, fetch all links inside elements with class prefetch
• [ ] Add support for pagination and links relations, https://github.com/joomlatools/joomlatools-pages/issues/452

Resources:

• https://github.com/joomlatools/joomlatools-framework/blob/1.0/code/media/lib_koowa/js/koowa.js
• https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver
• https://developers.google.com/web/updates/2017/09/abortable-fetch

Web workers

• https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Using_web_workers
• https://dev.to/trezy/loading-images-with-web-workers-49ap
• https://github.com/developit/greenlet
• https://github.com/developit/workerize
• https://github.com/GoogleChromeLabs/comlink
• https://github.com/GoogleChromeLabs/clooney
• https://medium.com/google-developer-experts/running-fetch-in-a-web-worker-700dc33ac854
• https://vanillajstoolkit.com/boilerplates/umd/
• https://github.com/jcubic/wayne