Parity: Add support for `example.org/path` cosmetic rules

[ameshkov]

Issue Details

uBO added support for specifying path in cosmetic rules: gorhill/uBlock@8b696a691a

In order to maintain parity we need to support this in CoreLibs as well.

Proposed solution

• We can internally convert it to $path modifier.
• We will need to update the documentation in the knowledge base

• Linked tsurlfilter issue: Parity: Add support for example.org/path cosmetic rules tsurlfilter#169
• Linked CoreLibs issue: Parity: Add support for example.org/path cosmetic rules CoreLibs#2012