Changelog for filter subscriptions

This feature might not exist in any other product or extensions. AdGuardHome top opensource software for **widely use**, we interest to see it write changelog for every subscribed filters separately about which rules added and removed by blocklist maintainer. (atleast keep log history about 3 or 5 recent changes and option to view them within webui or data folder if uncomfortable to implement)

I believe that's not hard to compare new downloads with local file and add to log whatever changes on it. beside, actually great rather than know nothing about what happening even it listed on public repository usually no specific intention to check them hardly) sometimes also may help us to collect necessary domains discarded from blocklists and create our own.

- [x] I checked to make sure that this issue has not already been filed