docs: add per-language custom instruction links to FAQ (#740)

Add links to the language-specific Copilot custom instructions for Node.js, Python, .NET, and Go under the FAQ section. Also removes a broken collection link.

Co-authored-by: Kiran Kashyap <kiran.kashyap.ds@example.com>
Co-authored-by: Patrick Nikoletich <patniko@github.com>

Author: 3 people

README.md

@@ -91,7 +91,12 @@ Yes, the GitHub Copilot SDK allows you to define custom agents, skills, and tool
 
 ### Are there instructions for Copilot to speed up development with the SDK?
 
-Yes, check out the custom instructions at [`github/awesome-copilot`](https://github.com/github/awesome-copilot/tree/main/instructions).
+Yes, check out the custom instructions for each SDK:
+
+- **[Node.js / TypeScript](https://github.com/github/awesome-copilot/blob/main/instructions/copilot-sdk-nodejs.instructions.md)**
+- **[Python](https://github.com/github/awesome-copilot/blob/main/instructions/copilot-sdk-python.instructions.md)**
+- **[.NET](https://github.com/github/awesome-copilot/blob/main/instructions/copilot-sdk-csharp.instructions.md)**
+- **[Go](https://github.com/github/awesome-copilot/blob/main/instructions/copilot-sdk-go.instructions.md)**
 
 ### What models are supported?