Copilot - Reimagine Prompts

[raffertyuy]

Reimagine prompt files according to the latest features of GitHub Copilot.

Here are some high-level thoughts

• copilot-instructions.md should contain a general system prompts
• .github/instructions/ should contain at least one for *.tf for terraform prompts
• Explore the right balance in creating reusable prompt files (.github/prompts/) and custom modes (.github/chatmodes/)
• Also explore where MCP servers will apply

Make this very effective for VSCode, then optimize for the GitHub Copilot Coding Agent.