Update documentation for this [page](https://github.com/javascript-tutorial/en.javascript.info/blob/52c1e61915bc8970a950a3f59bd845827e49b4bf/2-ui/5-loading/01-onload-ondomcontentloaded/article.md#page-domcontentloaded-load-beforeunload-unload) including examples from [sendBeacon](https://developer.mozilla.org/en-US/docs/Web/API/Navigator/sendBeacon) Or maybe have a separate document that covers this.
Update documentation for this page including examples from sendBeacon
Or maybe have a separate document that covers this.