Fetch doesn’t support custom parameters

I'm trying to fetch code from a third party library but I realised I can’t send a custom header.
```js
fetch(config.domURL).then((response) => response.text()),
fetch(config.authorURL).then((response) => response.text()),
```

Could this be considered to be added in the future?

Also as a question, when I try to load a script from another domain it doesn’t execute and I assuming it has to do with a security policy.
As the **sec-fetch-dest** is being set as **empty**.
Do you know if this is related to be using _fetch_ inside workers?

No file or test is named. Start by tracing the worker-dom fetch entry point and inspect how request options and headers are handled; separately investigate the worker script-loading path and its security-policy behavior. Done should define whether custom headers are supported and document or test the observed cross-domain script behavior.

Written by the indexing model from the issue text.