feat: Add support for badge widget

[divyanshub024]

Description

Add support for the Badge widget in Stac, enabling developers to declare badges in Server Driven UI for Flutter apps. This widget will allow displaying material design badge elements as described in the official documentation: Flutter Badge Widget.

Requirements

• Create a model for the Badge widget in the stac_core package.
• Add a parser for the Badge widget in the stac package.
• Create an example in Stac Gallery.
• Add documentation for the Badge widget.

Additional Context

Badges are commonly used for status, indicators, or counts, and proper support expands UI capabilities. See API for widget details: https://api.flutter.dev/flutter/material/Badge-class.html

[kumar-gautam24]

Hi , I would like to work on this issue, i have started exploring the current codebase and understanding it's standards

[divyanshub024]

Thank you @kumar-gautam24 !! I've assigned the issue to you. Feel free to reach out if you need any help 🙌🏻