Reth archival node guide

Reth and the Lighthouse consensus client can be installed on an Ubuntu machine to run an archival node, a method the guide describes as not the best way but one that works. Assembling the NUC took about 15 minutes, and the initial sync has 12 stages, with stage 4 the longest at about 4 days. After syncing, Reth serves RPC on 127.0.0.1:8545, and the guide shows a sample eth_blockNumber query and how to connect MetaMask via Tailscale and an SSH tunnel.