Bump WordPress/action-wp-playground-pr-preview from 2 to 3

[dependabot]

Bumps WordPress/action-wp-playground-pr-preview from 2 to 3.

Release notes

Sourced from WordPress/action-wp-playground-pr-preview's releases.

v3

Adds fork-safe reusable workflows for build-step WordPress Playground PR previews.\n\n- preview-build.yml builds and bundles one or more plugin/theme zips from pull_request runs.\n- preview-publish.yml publishes successful workflow_run artifacts to public release URLs and posts the Preview button.\n- README documents v3 quick starts, fork-safety, live same-repo and fork examples, Plugin Check-style usage, and migration notes.\n- Fixes release asset cleanup to sort by the GitHub CLI createdAt field.\n\nThe v2 tag remains unchanged for existing users.

Commits

• 43fc435 Tighten README wording (#79)
• 146f397 Simplify v3 README heads-up
• 40530b3 Fix release asset cleanup timestamp field
• 04f3eaf Fix template button diff-check whitespace
• 76d0b70 Skip immutable publishing for major-only tags
• 28e1c3b Fix immutable action publisher reference
• a5cb047 Reusable workflows for build-step plugin/theme previews
• See full diff in compare view

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