## AvaloniaUI/Avalonia — itemssource-checkpoint1…itemssource-checkpoint2

_17 commits._

### Backend
- **WIP** (26aa099)
- **WIP** (b8b3f15)
- **WIP** (490f6f7)
- **WIP** (3f04dd0)
- **WIP** (961d35b)
- **WIP** (da52258)
- **WIP** (4b49435)
- **WIP** (5af4252)
- **WIP** (645b37a)
- **WIP** (94e8f73)
- **WIP** (e22921b)
- **WIP** (9764e26)
- **WIP** (11adb87)
- **WIP** (076b362)
- **WIP** (ad6ab8c)
- **Update .gitignore** (1790ef1)
- **Expose pre/post collection changed events.** (21574f5)

_Recap by [Repo Wrapped](https://repowrapped.com/gh/AvaloniaUI/Avalonia?utm_source=github-action)._