Feature: Built-in event category filtering with toggle UI

[thbst16]

Description

When building timelines with many events spanning different categories (e.g., "Super Bowls", "Expansion Teams", "Rule Changes"), users need a way to filter the view to focus on specific event types.

Use Case

My NFL timeline has 40+ events across categories like founding events, championship games, team expansions, and rule changes. Users should be able to toggle categories on/off to focus on what interests them.

Proposed Solution

• Add an optional category property to the event data structure
• Provide a showCategoryFilter prop that renders a toggle UI
• Support onCategoryChange callback for custom filter implementations
• Allow styling of category chips/toggles via theme

Example API

<Timeline
  data={data}  // events include { category: 'super-bowl' }
  showCategoryFilter={true}
  categoryLabels={{ 'super-bowl': 'Super Bowls', 'expansion': 'Expansion Teams' }}
/>

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Issue generated from user feedback while building an NFL history timeline