Add Copilot setup instructions and workflow for effective collaboration

[Copilot]

This PR implements the necessary setup files to enable GitHub Copilot to effectively collaborate on the Figma Batch Styler project by providing comprehensive environment configuration and architectural guidance.

Changes Made

🔧 GitHub Workflow (.github/workflows/copilot-setup-steps.yaml)

Added a complete environment setup workflow that configures:

• Node.js 18 with npm caching
• Dependency installation via npm install
• Project build process (with error handling for known issues)
• Project structure and configuration verification
• Ready-to-use environment for Copilot development

📚 Copilot Instructions (.github/copilot-instructions.md)

Created comprehensive technical documentation covering:

• Project Overview: Figma plugin for batch updating text and color styles
• Architecture: Svelte 3.x + TypeScript frontend with Figma Plugin API backend
• Key Files: Main plugin logic (code.ts), UI components, build configuration
• Development Workflow: Install, build, and development patterns
• Code Style: TypeScript patterns, Svelte reactivity, async Figma API usage

⚠️ Known Issues & Limitations

Critical Build Issue: The project currently fails to build due to a compatibility issue with the svelte-color dependency:

ParseError: Attributes need to be unique
node_modules/svelte-color/Hue.svelte:38
<div class="hue {className}" class:vertical class:horizontal={!vertical}>
  <Slider bind:value={sliderValue} value={sliderValue} {vertical} on:input={handle}/>
                                     ^

No Test Infrastructure: The project lacks any automated testing, limiting Copilot's ability to validate changes.

Legacy Dependencies: Several deprecated packages may cause future compatibility issues.

🚀 Next Steps

Dev Team Action Required: Please test the Copilot integration by commenting:

@copilot Please try building and testing this project using the new setup workflow and instructions. Let us know what issues you encounter and how well the setup helps you understand the codebase.

This will validate:

• Whether Copilot can navigate the build issues effectively
• How well the instructions guide Copilot's understanding
• What additional guidance may be needed for optimal collaboration

The setup provides Copilot with all necessary context to work with this Figma plugin codebase while being transparent about current limitations.

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

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