feat: ToolBar controls

[Kryptos-FR]

PR Details

Adds ToolBar and ToolBarTray which don't exist in Avalonia (see AvaloniaUI/Avalonia#705).

Notes

The current implementation is basic and is no different to using nested StackPanels. Later, we can implement the overflow s well as moving, dragging/dropping separate ToolBars.

Types of changes

• Docs change / refactoring / dependency upgrade
• 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)

Checklist

• My change requires a change to the documentation.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have built and run the editor to try this change out.