Improve prevent-fetch — set response.status to 0 if responseType is set to opaque

[AdamWr]

Related to - AdguardTeam/AdguardFilters#163224

Steps to reproduce:

1. Add this rule:

example.org#%#//scriptlet('prevent-fetch', 'pagead2.googlesyndication.com', '', 'opaque')

2. Go to - https://example.org/
3. Run in console:

const request = new Request('https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js', {
  method: 'HEAD',
  mode: 'no-cors'
});
const response = await fetch(request);
if (response.status !== 0) {
  alert('adblock');
}

With scriptlet enabled response.status is 200 so alert is displayed, but as far as I understand, if response.type is opaque, then response.status should be 0:

An opaque filtered response is a filtered response whose type is "opaque", URL list is « », status is 0, status message is the empty byte sequence, header list is « », body is null, and body info is a new response body info.

https://fetch.spec.whatwg.org/#concept-filtered-response-opaque

So maybe we could set status basing on responseType:

Scriptlets/src/helpers/noop-utils.ts

Lines 99 to 102 in 6c3693f

	const response = new Response(responseBody, {
	status: 200,
	statusText: 'OK',
	});

Perhaps also response.statusText should be set to '' and response.body to null, if responseType is set to opaque.

[AdamWr]

Also allow to set responseBody to empty string '':

Scriptlets/src/scriptlets/prevent-fetch.js

Lines 123 to 131 in 40fd803

	let strResponseBody;
	if (responseBody === '' || responseBody === 'emptyObj') {
	strResponseBody = '{}';
	} else if (responseBody === 'emptyArr') {
	strResponseBody = '[]';
	} else {
	logMessage(source, `Invalid responseBody parameter: '${responseBody}'`);
	return;
	}

Related to this - AdguardTeam/AdguardFilters#166464

It looks like that website is checking if content of the response is ''.
Something like (just simple example):

const fetchTest = await fetch('/test');
const content = await fetchTest.text();
const expectedResponse = '';
if(content !== expectedResponse) {
  adblock
}