Require YouTrack issue reference in PRs

[kropp]

Describe proposed changes and the issue being fixed

(Optional) Fixes [link to the issue]

Testing

(Optional) Describe how you tested your changes (provide a snippet or/and steps)

(Optional) This should be tested by QA

Release Notes

Section - Subsection

• Describe change in format https://github.com/JetBrains/compose-multiplatform/blob/master/tools/changelog/PR_FORMAT.md
  • Sections: Highlights, Known Issues, Breaking Changes, Migration Notes, Features, Fixes
  • Subsections: Multiple Platforms, iOS, Desktop, Web, Android, Resources, Gradle Plugin, Lifecycle, Navigation, SavedState