vanilla-framework v4.55.0 release notes

chore: skip Percy on Blocked PRs even with the Percy label by @Onibenjo in https://github.com/canonical/vanilla-framework/pull/5812
feat: Update position of CTA block in Tiered list and Equal heights patterns by @muhammad-ali-pk in https://github.com/canonical/vanilla-framework/pull/5816
Update Content Card to accept stacked_image param and for content_type to accept lists by @petesfrench in https://github.com/canonical/vanilla-framework/pull/5819

Full Changelog: https://github.com/canonical/vanilla-framework/compare/v4.52.0...v4.55.0