lith env.example: document Cloudflare cache-purge vars
Without CLOUDFLARE_PURGE_TOKEN + CLOUDFLARE_ZONE_ID set, lith/webhook.sh
silently skips the edge purge after deploy and stale responses can
persist for up to 4h (default static-asset TTL). Document both vars
in the example with a pointer to scoped-token creation so a fresh
lith setup doesn't ship with a broken purge path.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>