Bug with WebWorker loading of 814.ffmpeg.js + solution

**Describe the bug**
There are two errors I get `NS_ERROR_BLOCKED_BY_POLICY` or something like incorrect origin. This bug when creating `new Worker()` from multithreaded `814.ffmpeg.js` URL

**To Reproduce**
Idk, just upload to server and try to use

**Expected behavior**
WebWorker starting without problems

- Browser Firefox

**Additional context**
So I found solution, in `ffmpeg/package/dist/umd/ffmpeg.js` instead of:
```js
new Worker(new URL(e.p + e.u(814), e.b),{ type: void 0 })
```
use:
```js
new Worker(getWorkerURL(new URL(e.p + e.u(814), e.b)),{ type: void 0 })
```

and `getWorkerURL` function:
```js
function getWorkerURL(e) {
const t = `importScripts( "${e}" );`;
return URL.createObjectURL(new Blob([t], { type: "text/javascript" }));
}
```
Don't know where I can fix this in whole source code, so leave this as issue. Think that can help someone.