Add support for `$to` and `$from` modifiers

`$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.

**UPD2:** for `$to` I suggest using `if-frame-url`, but we should keep in mind that it cannot be mixed with any `unless-*` property.