Added Event Schema Versioning samples

Shows how to handle basic event schema versioning scenarios using event and stream transformations (e.g. upcasting):

• Simple mapping
  • New not required property
  • New required property
  • Renamed property
• Upcasting
  • Changed Structure
  • New required property
• Downcasters
• Events Transformations
• Stream Transformation
• Summary
• 📝 Simple patterns for events schema versioning

See also PR: #18