feat: Add support for border side in BoxDecoration

[MohamedAbd0]

Description

Adds support for individual border sides in StacBorder, allowing users to specify different BorderSide properties for top, bottom, left, and right borders instead of being limited to Border.all().

• Enhanced StacBorder class with individual border side properties:
  • top: StacBorderSide?
  • right: StacBorderSide?
  • bottom: StacBorderSide?
  • left: StacBorderSide?
• Backward compatibility maintained with existing Border.all() properties
• Smart parsing logic that detects when individual sides are used vs legacy properties
• Added comprehensive border documentation (website/docs/styles/border.md)
• Updated existing border side documentation with cross-references

Related Issues

Closes #290

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

[CLAassistant]

All committers have signed the CLA.

[MohamedAbd0]

Hi @divyanshub024 , Notes fixed

[divyanshub024]

As always, Thanks for such great work 💯 🎉