test(previews): add end-to-end tests

[ahuseyn]

Description

This PR adds E2E test suite to the plugin. It uses Playwright and @wordpress/e2e-test-utils-playwright. Testing covers settings page, preview links and Faust integration. This PR also adds a GitHub workflow to automate the e2e testing.

Related Issue

• test(previews): Add E2E tests #228

Dependant PRs

N/A

Type of Change

• ✅ Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactoring (no functional changes)
• 📄 Example update (no functional changes)
• 📝 Documentation update
• 🔍 Performance improvement
• 🧪 Test update

How Has This Been Tested?

Screenshots

Checklist

• I have read the CONTRIBUTING document
• My code follows the project's coding standards
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works (if applicable)
• Any dependent changes have been highlighted, merged or published

[github-actions]

ℹ️ Download the hwp-previews plugin artifact from this workflow run (see the 'Artifacts' section at the bottom).

[github-actions]

ℹ️ Download the hwp-previews plugin artifact from this workflow run (see the 'Artifacts' section at the bottom).

[github-actions]

ℹ️ Download the latest hwp-previews plugin zip from this PR
(See the 'Artifacts' section at the bottom)

[colinmurphy]

LGTM 🚀 🚀 🚀