Solve 'SyntaxError: import declarations may only appear at top level of a module' in Firefox

[pjlammertyn]

cfr vitejs/vite#4586

already tried: sveltejs/kit#9528

const DataTableWorker = await import('$lib/workers/DataTable.worker?worker')
this.worker = new DataTableWorker.default()

//can also be written as 

import workerUrl from '$lib/workers/DataTable.worker?url';
this.worker = new Worker(workerUrl, { type: 'module' });