feat(color): add support for RGBA color representation and methods

[AshAnand34]

Description

This pull request introduces an opacity parameter to various annotators in the supervision/annotators/core.py file, enabling control over the transparency of overlay masks. It also refines the color handling by switching from as_bgr() to as_bgra() to support alpha channels. Additionally, input validation has been added to ensure the scene parameter is not None.

Enhancements to Annotators:

• Opacity Parameter Added: Introduced an opacity parameter (default 0.5) to all annotators, allowing users to control the transparency of overlay masks. This parameter is validated to ensure values are between 0 and 1.

• Overlay Blending: Updated the annotate methods to blend overlays with the original scene using cv2.addWeighted, incorporating the new opacity parameter for smooth transparency effects.

Improvements to Color Handling:

• Alpha Channel Support: Replaced color.as_bgr() with color.as_bgra() across all annotators to support alpha channels, which is essential for blending transparency.

Input Validation:

• Scene Parameter Check: Added validation to ensure the scene parameter is not None before proceeding with annotation. A ValueError is raised if this condition is not met.

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

Any specific deployment considerations

For example, documentation changes, usability, usage/costs, secrets, etc.

Docs

• Docs updated? What were the changes: