feat(xo-stack): add text-ellipsis utility class

[OlivierFL]

Description

Add .text-ellipsis utility class to avoid duplicating CSS in components that need text ellipses.

Checklist

• Commit
  • Title follows commit conventions
  • Reference the relevant issue (Fixes #007, See xoa-support#42, See https://...)
  • If bug fix, add Introduced by
• Changelog
  • If visible by XOA users, add changelog entry
  • Update "Packages to release" in CHANGELOG.unreleased.md
• PR
  • If UI changes, add screenshots
  • If not finished or not tested, open as Draft