feat: pass ToastShowParams to onShow callback

[yagiz2000]

Summary

• Pass ToastShowParams to the onShow callback so consumers can access toast data (type, text, props, etc.) when a toast is shown
• Updated type definitions for both ToastOptions and ToastProps

Closes #587

Test plan

• Verify onShow callback receives the correct ToastShowParams when a toast is shown
• Verify existing usage without onShow params still works (backward compatible)
• Verify TypeScript types are correct

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