docs: random docs improvements

[reidbarber]

• Add dynamic favicon based on current library
• Add icons to "Copy Page as Markdown" menu
• Replace inline styles in examples with style macro usage
• Update Picker usage to use onChange / value

✅ Pull Request Checklist:

• Included link to corresponding React Spectrum GitHub Issue.
• Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• Filled out test instructions.
• Updated documentation (if it already exists for this component).
• Looked at the Accessibility Practices for this feature - Aria Practices

📝 Test Instructions:

🧢 Your Project:

[rspbot]

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