Add doc validation workflow + fix linting errors

[josbeir]

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[Copilot]

Pull request overview

This PR adds an automated documentation validation workflow for the docs/ subtree and updates the docs sources to satisfy formatting/linting requirements (code-fence language tags and heading/list formatting), alongside a small Node/VitePress config compatibility tweak.

Changes:

• Add a GitHub Actions workflow to validate documentation changes on PRs and on pushes to 4.x.
• Switch the docs Node package to ESM ("type": "module") to align with the ESM-based VitePress config.
• Normalize markdown formatting across multiple pages (language-tagged code fences, list/heading formatting).

Reviewed changes

Copilot reviewed 4 out of 18 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
.github/workflows/docs-validation.yml	Adds a reusable-workflow-based docs validation job for changes under docs/** / .github/**.
docs/package.json	Switches the docs package to ESM (type: module) to match the VitePress config module format.
docs/en/view-helper.md	Normalizes PHP code-fence language tags ( ```php).
docs/en/url-checkers.md	Normalizes PHP code-fence language tags ( ```php).
docs/en/upgrade-3-to-4.md	Normalizes code-fence language tags and list formatting in migration tips.
docs/en/upgrade-2-to-3.md	Normalizes bash code-fence language tag ( ```bash).
docs/en/testing.md	Normalizes PHP code-fence language tags ( ```php).
docs/en/redirect-validation.md	Normalizes text/php code-fence language tags and numbered-list formatting.
docs/en/password-hashers.md	Normalizes PHP code-fence language tags ( ```php).
docs/en/migration-from-the-authcomponent.md	Normalizes PHP code-fence language tags ( ```php).
docs/en/middleware.md	Normalizes PHP code-fence language tags ( ```php).
docs/en/index.md	Normalizes bash/shell/php code-fence language tags ( ```bash, ```shell, ```php).
docs/en/impersonation.md	Normalizes PHP code-fence language tags and numbered-list formatting.
docs/en/identity-object.md	Normalizes php/text code-fence language tags.
docs/en/identifiers.md	Normalizes PHP code-fence language tags ( ```php).
docs/en/contents.md	Adjusts heading level for consistency (## instead of ###).
docs/en/authenticators.md	Normalizes code-fence language tags ( ```php, ```text) and trims an extra blank line.
docs/en/authentication-component.md	Normalizes PHP code-fence language tags ( ```php).

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