Improve the comparison with Pi-hole in the README.

[DandelionSprout]

Prerequisites

• I have checked the Wiki and Discussions and found no answer

• I have searched other issues and found no duplicates

• 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.