Clarify import requirements for Xcode projects

Added note about importing .github directory for Xcode projects.

Author: michaelversus

Docs/CustomInstructions.md

@@ -23,6 +23,7 @@ GitHub Copilot for Xcode supports two types of Markdown-based instructions files
 Whitespace between instructions is ignored, so the instructions can be written as a single paragraph, each on a new line, or separated by blank lines for legibility.
 
 Reference specific context, such as files or URLs, in your instructions by using Markdown links.
+You need to import `.github/` directory and all referenced files inside your xcode project/workspace if your instructions are pointing to extra files.
 
 ## Custom instructions examples
 
@@ -180,4 +181,4 @@ To modify or view an existing instructions file, click **Open Instructions Folde
 
 ## Related content
 
-* [Community contributed instructions, prompts, and chat modes](https://github.com/github/awesome-copilot)
+* [Community contributed instructions, prompts, and chat modes](https://github.com/github/awesome-copilot)