Mock `navigator.sendBeacon` and modify its request body

[piquark6046]

To reduce the browser fingerprinting without a breakage, we can randomize or modify any request body of navigator.sendBeacon.

AdguardTeam/AdguardFilters#200689

[ameshkov]

Why can't we simply mock it as noop function using existing scriptlets?

[piquark6046]

#484 (comment)
Already tried. But, I face a breakage if I try.

[ameshkov]

This is super strange, in theory sendBeacon is supposed to be "call & forget" type of function

[piquark6046]

#484 (comment)
It seems that they check cookie of its navigator.sendBeacon response at the server