Stricter YouTube safe search

### Prerequisites

- [X] I have checked the [Wiki](https://github.com/AdguardTeam/AdGuardHome/wiki) and [Discussions](https://github.com/AdguardTeam/AdGuardHome/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

https://www.google.com/supported_domains

This appears to be the list of google owned domains.

For YouTube restriction you might think about offering a modifier for restrict.youtube vs restrictmoderate.youtube.

I am very content with the restrict..

https://github.com/AdguardTeam/AdGuardHome/commits/fc7d93b920b196e654502e1a2b720d56bae05711/dnsfilter/safesearch.go