add adguard to dns section (#3947)

Co-authored-by: Klaus Zerwes <Klaus.Zerwes@rosalux.org>
Co-authored-by: Kieran <32241933+KieranRobson@users.noreply.github.com>
Co-authored-by: nodiscc <nodiscc@gmail.com>

README.md

@@ -751,6 +751,7 @@ _See also: [dbdb.io - Database of Databases](https://dbdb.io/)_
 
 _See also: [awesome-sysadmin/DNS - Servers](https://github.com/awesome-foss/awesome-sysadmin#dns---servers), [awesome-sysadmin/DNS - Control Panels & Domain Management](https://github.com/awesome-foss/awesome-sysadmin#dns---control-panels--domain-management)_
 
+- [AdGuard Home](https://adguard.com/en/adguard-home/overview.html) - Free and open source, userfriendly ads & trackers blocking DNS server. ([Source Code](https://github.com/AdguardTeam/AdGuardHome)) `GPL-3.0` `Docker`
 - [blocky](https://github.com/0xERR0R/blocky) - Fast and lightweight DNS proxy (like Pi-hole) as ad-blocker for local network with many features. `Apache-2.0` `Go`
 - [Maza ad blocking](https://maza-ad-blocking.andros.dev/) - Local ad blocker. Like Pi-hole but local and using your operating system. ([Source Code](https://github.com/tanrax/maza-ad-blocking)) `Apache-2.0` `Bash`
 - [Pi-hole](https://pi-hole.net/) - A blackhole for Internet qdvertisements with a GUI for management and monitoring. ([Source Code](https://github.com/pi-hole/pi-hole)) `EUPL-1.2` `Shell/PHP`