DEMO: Move this slider to set the progress attribute on all these Custom Elements:
Even though the grey elements (<x-foo>, defined in worklet.js) intentionally block for 500ms in a while() loop, the page and elements backed by other Element Worklets are unaffected.
<x-foo> is a Custom Element registered via customElements.addModule():<x-foo-2> is a second worklet module, which can run on a separate thread: