Avoid duplicate in blocklist

[TroySigX]

Prerequisites

• [X] I have checked the Wiki and Discussions and found no answer

• [X] I have searched other issues and found no duplicates

• [X] I want to request a feature or enhancement and not ask a question

Description

What problem are you trying to solve?

When I add a new blocklist, I want to know what percentage of domains of that new blocklist is already blocked by my existing ones, to avoid duplication.

Proposed solution

For each blocking rule (||example.org), check if it is already blocked. If the new blocklist has rule ||example.org^ but exisiting blocklists only have ||example.org$third-party (or something similar), then it is not considered blocked by the old lists.