Add support for $to and $from modifiers

[ameshkov]

$to is a modifier that's applied to the request URL's domain name:
https://adguard.com/kb/general/ad-filtering/create-own-filters/#to-modifier

$from is just an alias for $domain

I am not entirely sure that $to can be implemented in Safari content blockers though, if-domain may only be applied to the main document domain, needs to be tested.

UPD: quick test shows that if-domain won't work indeed. Anyways, let's keep this issue open, maybe you can come up with an alternative solution.