The README now covers what keepalive is, a quick start, the adapter table,
and links. Reference material moves to docs/: configuration (every option,
per-adapter keys, validation), deployment (Compose, Coolify, Docker, source),
how it works (writes, retries, timeouts, logging), known issues (PostgreSQL
public-schema permissions and Aiven's ACL key-pattern tilde, by log line),
and adding an adapter (now including ConfigKeys registration).
.gitignore also excludes config.yaml, matching .dockerignore.
