Improve the comparison with Pi-hole in the README.

### 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

### The problem

I've noticed that there's still a lot of people on the internet who still think Pi-hole is any good, so I'm proposing adding additional info to https://github.com/AdguardTeam/AdGuardHome#comparison-pi-hole to cover additional details.
* Clarifying the "Cross-platform" row (The most important part of these proposals).
* Added info on AGH being able to block by IP and CIDR entries.
* Added 1 mention of DNS-over-QUIC support.

### Proposed solution

Change:
```
| Cross-platform | ✅ | ❌ (not natively, only via Docker) |
| Running as a DNS-over-HTTPS or DNS-over-TLS server | ✅ | ❌ (requires additional software) |
| Blocking phishing and malware domains | ✅ | ❌ (requires non-default blocklists) |
| Parental control (blocking adult domains) | ✅ | ❌ (requires non-default blocklists) |
| Force Safe search on search engines | ✅ | ❌ |
| Per-client (device) configuration | ✅ | ✅ |
| Access settings (choose who can use AGH DNS) | ✅ | ❌ |
| Running [without root privileges][wiki-noroot] | ✅ | ❌ |
```
↓ ↓ ↓ ↓ ↓
```
| Cross-platform, including Windows and macOS | ✅ | ❌ (not natively, only via Docker) |
| Running as a DNS-over-HTTPS, DNS-over-TLS, or DNS-over-QUIC server | ✅ | ❌ (requires additional software) |
| Blocking phishing and malware domains | ✅ | ❌ (requires non-default blocklists) |
| Parental control (blocking adult domains) | ✅ | ❌ (requires non-default blocklists) |
| Force Safe search on search engines | ✅ | ❌ |
| Per-client (device) configuration | ✅ | ✅ |
| Access settings (choose who can use AGH DNS) | ✅ | ❌ |
| Running [without root privileges][wiki-noroot] | ✅ | ❌ |
| Blocking ads and trackers with IP address rules | ✅ | ❌ |
| Blocking ads and trackers by CNAME | ✅ | ❌ |
```

### Alternatives considered and additional information

No alternatives that I am currently aware of.