Add support for `path` modifier

[rakleed]

Problem Description

Extended CSS rules put a lot of load on the site, and many modern sites obfuscate their code. And when sites like yandex.ru have a lot of pages, then for such a site, to reduce the load from extended CSS, it would be good to apply rules only for certain pages.

Proposed Solution

Add support for path modifier.

Alternatives Considered

Additional Information

The path modifier is already supported by AdGuard for Windows, macOS, Android and Browser Extension for Chrome, Edge and Firefox.

[ameshkov]

This can be done for extended CSS rules if it hasn't been already done.

For Safari rules it's been already done: https://github.com/AdguardTeam/SafariConverterLib/issues/30