docs: Holesky on WSL2 (reth + Lighthouse) — docker.sock, DNS & --allow-insecure-genesis-sync

[hieudao151093]

Environment: Windows 11 + WSL2 Ubuntu 24.04 (systemd enabled), Rust 1.90, Docker 28.2.2, Lighthouse v8.

Issues met:

• docker.sock permission denied on WSL2
• DNS failing for Holesky checkpoint endpoints inside container
• chainspec mismatch when reusing a datadir
• Lighthouse v8 requires --allow-insecure-genesis-sync when not using checkpoint

This PR adds a short WSL2 Holesky guide and troubleshooting notes (Docker group + WSL shutdown, DNS flags/alternate checkpoint URLs, fresh datadir note, and the v8 genesis-sync flag).

[hieudao151093]

Hi, this adds a small WSL2 Holesky guide + troubleshooting for docker.sock/DNS/chainspec/Lighthouse v8 genesis sync.
Happy to iterate on any feedback. Thanks!

[hieudao151093]

Summary — Adds a WSL2 Holesky quickstart for reth (execution) + Lighthouse (beacon) with practical troubleshooting:

• docker.sock permissions on WSL2
• DNS failures for checkpoint endpoints inside Docker
• chainspec mismatch when switching networks
• Lighthouse v8 requiring --allow-insecure-genesis-sync for genesis sync

Tested — Windows 11 + WSL2 Ubuntu 24.04 (systemd), Docker 28.2.2, Rust 1.90, Lighthouse v8.

Happy to iterate on any feedback!

[dubai199999]

Tested on another Win11 laptop; same result

[Ajinomoto6789]

tested nothing changed

[theblackoreo]

win10 nothing