feat: add platform validation for widget support in Stac class

[felipecastrosales]

Here's the documentation in English:

Description

Implemented new platform-specific widgets functionality in the Stac framework. It's now possible to specify on which platforms a widget should be rendered through the platform property in JSON.

Features:

• platform property: Can be a single string or a list of strings
• Automatic validation: Checks if the current platform is in the allowed list
• Logging: When platform is not supported, returns null and logs an informative message
• Supported platforms: android, fuchsia, ios, linux, macos, windows

Usage examples:

Multiple platforms:

{
  "platform": ["android", "ios"],
  "type": "text",
  "data": "Widget only for mobile"
}

Single platform:

{
  "platform": "android",
  "type": "text",
  "data": "Widget only for Android"
}

Behavior:

• If current platform is allowed: widget renders normally
• If current platform is NOT allowed: returns null and logs:

  Widget not supported on platform [linux]. Only available for: android, ios
  

Related Issues

Closes #

Type of Change

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to change)
• Code refactor
• Build configuration change
• Documentation
• Chore