[FEATURE] Add blur command for images

[Maelkiz]

🚀 Feature Request

Add a blur command to simply-edit that allows users to apply blur effects to images.

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🎯 Problem / Motivation

Currently, simply-edit supports various image manipulation tasks like flip, rotate, invert, and grayscale conversion. A blur command would expand the toolkit to include common image effects that users frequently need for everyday image tasks.

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💡 Proposed Solution

Implement a blur command that allows users to apply blur effects to images. The implementation details, including:

• Command syntax and options
• Blur types and intensity levels (e.g., Gaussian blur, motion blur, box blur)
• Default blur parameters
• Error handling

...are left to the developer's discretion to determine the best approach for the simply-edit CLI.

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✅ Acceptance Criteria

• Blur command is implemented and functional
• Command integrates seamlessly with the existing simply-edit CLI
• Blurred images can be output in supported formats (PNG, JPG, ICO, SVG)
• Documentation is updated to reflect the new blur command

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🧠 Notes / Context (if applicable)

This feature would complement the existing image manipulation capabilities and provide users with a more complete toolkit for everyday image tasks.