docs: add tutorial for disabling ID storage

[DavidWells]

Add comprehensive documentation explaining how to disable anonymous ID and user ID storage for privacy compliance.

This tutorial covers:

• Using @analytics/core vs main package
• Clear code examples showing with/without storage
• Benefits and considerations of disabling ID storage
• Custom storage configuration options
• Plugin considerations for privacy
• Testing guidance
• When to use this approach

Fixes #466

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