feat: add direction prop to PaperProvider and useLocale hook for RTL support

[hristototov]

Motivation

Components in react-native-paper read RTL state directly from
I18nManager.getConstants().isRTL. This has two issues:

• I18nManager is a no-op on React Native Web, so RTL breaks entirely on Web
• The value is read at module load or render time with no way to override it reactively

Solution

New: useLocale() hook

import { useLocale } from 'react-native-paper';

const { direction } = useLocale(); // 'ltr' | 'rtl'

<PaperProvider direction="rtl">
  {children}
</PaperProvider>

Defaults to I18nManager.getConstants().isRTL when not provided, so existing apps are unaffected. Setting the prop does not call I18nManager.forceRTL or modify any native state; it only tells Paper which direction to use for rendering.

Related issue

N/A
Notion link

Test plan

• Add direction="rtl" to PaperProvider in the example app and verify RTL layout renders correctly across components
  Remove the prop and verify the app falls back to I18nManager (default behaviour unchanged)
• On React Native Web, set direction="rtl" and verify RTL layout works
• All existing tests pass (yarn test)

[github-actions]

The mobile version of example app from this branch is ready! You can see it here.