Document a note about `static:warm` and Cloudflare

From a discussion on Discord: https://discord.com/channels/489818810157891584/489830745137872900/1395670738186276935

Cloudflare is more aggressively targeting bots (for the better or worse). This has been shown to affect cache warm operations.

A way around it is to add the server's own IP to a whitelist rule (specifics needed).