Update documentation for ArFoundation and Vuforia.

[timbotimbo]

Description

Updates the readme for both ARFoundation and Vuforia.

• I removed the Android instructions to manually include all libraries.
• Instruction for unityLibrary:xrmanifest.androidlib error.
• Added iOS section for Vuforia.
• Added a warning about the Flutter 3.22 crash on Android. #957

This replaces PR #906 and #911.

This should help with issues like

https://github.com/juicycleff/flutter-unity-view-widget/issues/844, https://github.com/juicycleff/flutter-unity-view-widget/issues/689, #904 and multiple other issues with the Vuforia label

@Ahmadre Since you recently had issues with Vuforia, maybe you can review this.

Type of Change

• [ ] ✨ New feature (non-breaking change which adds functionality)
• [ ] 🛠️ Bug fix (non-breaking change which fixes an issue)
• [ ] ❌ Breaking change (fix or feature that would cause existing functionality to change)
• [ ] 🧹 Code refactor
• [ ] ✅ Build configuration change
• [x] 📝 Documentation
• [ ] 🗑️ Chore