Add: label supprot for CurvedNavigationBarItems (Closes #11)

[satish-nep79]

Overview
This PR addresses the requirements specified in issue #11 by adding label support for the CurvedNavigationBar. It also allows for customizing the text style and visibility of active and inactive labels.

Details of the Change:

• Introduces a CurvedBarItem model to replace the basic list of widgets in the items. The model includes:
  • label: A text label for each navigation item.
  • child: It takes the widget to be displayed in the bottom bar
• activeLabelStyle and inActiveLabelStyle: Customizable text styles for active and inactive states.
• showActiveLabel and showInactiveLabel: Flags to control the visibility of labels based on the selected state.

Fixes & Improvements:

• Closes issue Adding a text below the icon #11 by enabling the requested label customization feature.
• Improves the user experience by allowing labels to be added and customizable

Testing:

• Verified that the CurvedNavigationBar renders correctly with labels on both active and inactive states.