Support js-yaml v5

[renatodeleao]

• Rollup Plugin Name: yaml
• Rollup Plugin Version: 5.0.0

Feature Use Case

Support new js-yaml@5.x parser and its new features

• https://github.com/nodeca/js-yaml/blob/master/CHANGELOG.md#500---2026-06-20
• https://github.com/nodeca/js-yaml/blob/master/docs/migrate_v4_to_v5.md

Feature Proposal

Not sure how you want to handle this version wise, but could be two releases or just one

v5.1.0

• upgrades js-yaml to v5, internally defaults YAML 1.1 schema. Everything stays the same besides the internal parser
• a small wrapper around load/loadAll functions will needs to be made so it doesn't throw on empty (new behaviour, compared to v4).

v6.0.0

Breaking change

• defaults to new YAML 1.2 schema if not specified
• allow consumers to pass loadOptions/parserOptions via the plugin config, which will be forward them to the internal YAML.load/YAML.loadAll calls.
  1. Move js-yaml as peerDependency instead of devDependency requiring explicit install, ensures that schemas can be imported from js-yaml at consumers and forward via parserOptions
  2. Or re-export the schemas and forward them through @rollup/plugin-yaml package.

Cheers ✌️