Function useViewportTracking

useViewportTracking(
options: UseViewportTrackingOptions,
): UseViewportTrackingReturn
Tracks whether an entry is visible in the viewport and fires entry view events with accumulated duration tracking.

The hook implements a three-phase event lifecycle per visibility cycle:
1. Initial event after accumulated visible time reaches viewTimeMs.
2. Periodic updates every viewDurationUpdateIntervalMs while visible.
3. Final event when visibility ends (only if at least one event was already emitted).
Parameters
- options: UseViewportTrackingOptions
  UseViewportTrackingOptions including the entry, thresholds, and selected optimization data.
Returns UseViewportTrackingReturn
An object with isVisible state and an onLayout callback for the tracked View
Throws
Error if called outside of an OptimizationProvider

Remarks
Uses useScrollContext if available, otherwise falls back to screen dimensions. A new visibility cycle (with a fresh viewId) starts each time the tracked entry transitions from invisible to visible. Time accumulation pauses when the app moves to the background.
Example
```
function TrackedEntry({ entry }: { entry: Entry }) {
  const { onLayout, isVisible } = useViewportTracking({
    entry,
    threshold: 0.8,
    viewTimeMs: 2000,
  })

  return (
    <View onLayout={onLayout}>
      <Text>{isVisible ? 'Visible' : 'Hidden'}</Text>
    </View>
  )
}
```
- Defined in packages/react-native-sdk/src/hooks/useViewportTracking.ts:228