Reformat README.md with correct markdown structure

[Copilot]

Pull Request Description

Changes Made

Corrected inaccuracies:

• Fixed project description (was incorrectly labeled as "gcp-kubernetes project")
• Updated script references from non-existent init.py to actual gproj script

Enhanced structure:

• Converted repository list to markdown table with descriptions
• Replaced broken CONTRIBUTING.md link with Additional Resources section (pull_request_template.md, copilot-instructions.md, security)
• Added Project Features section documenting multi-repo management, documentation integration, backup management, parallel operations
• Added Configuration section explaining .gproj file structure

Before:

- terraform-provider-smartprompt: smartprompt::terraform-provider-smartprompt
- smartprompt-api: smartprompt::smartprompt-api

After:

| Repository | Description |
|-----------|-------------|
| **terraform-provider-smartprompt** | Terraform provider for smartprompt |
| **smartprompt-api** | Backend API service |

Type of Change

• Documentation update

Checklist

• My code follows the project's coding standards
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

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