According to the YAML specification [^1]:
- > An anchored node need not be referenced by any alias nodes
This means that it's OK to declare anchors but don't have any alias
referencing them. However users could want to avoid this, so a new
option (e.g. `forbid-unused-anchors`) is implemented in this change.
It is disabled by default.
[^1]: https://yaml.org/spec/1.2.2/#692-node-anchors