[FEATURE] Add avatar component

[Defkon1]

Implement a BitAvatar component inspired by the design and UX of the Bootstrap Italia Avatar component.

Requirements:

Describe the list of requirements this feature needs:

• Create a reusable BitAvatar component following Bootstrap Italia's guidelines (docs).
• Support textual, images and link avatar
• Support color variants (primary, secondary, success, danger, warning, info, light, dark, etc.).
• Support user presence badge
• Support user status badge
• Support extra text
• Expose properties for text, short text, size and colors of the avatar and its main subcomponents.
• Expose parameters for ARIA/accessibility attributes.
• Ensure full accessibility including keyboard navigation, ARIA attributes, and screen reader support.
• Responsive design and mobile-friendly behavior.

Acceptance Criteria:

• The component renders valid Bootstrap Italia avatar markup.
• All documented variants and styles are supported via parameters.
• The component is unit tested for all major styles.
• Usage examples are provided in the documentation or a sample page.

References

• Bootstrap Italia - Avatars documentation (docs)