Add setup instructions and recommended skills to agents.md (including custom DeepSource skill)

[malek10xdev]

The current agents.md lacks guidance on setting up helpful AI skills, which can improve developer productivity and consistency.

We should document recommended skills and include a custom DeepSource skill under .agents/skills to standardize usage across the team.

Expected Behavior

• agents.md includes clear instructions on how to install and configure useful skills
• Recommended skills are listed with links and brief descriptions
• A custom DeepSource skill is added under .agents/skills and documented

Suggested Changes

• Update agents.md with setup instructions and recommended skills:
  • https://skills.sh/aj-geddes/useful-ai-prompts/design-patterns-implementation
  • https://skills.sh/obra/superpowers
  • https://skills.sh/github/awesome-copilot/javascript-typescript-jest
• Add a custom DeepSource skill inside .agents/skills
• Document how and when to use the DeepSource skill (e.g., code quality, static analysis, PR checks)