docs: update developer documentation and add README links

- Added links to developer READMEs in CUSTOM_TOOLS.md to guide users to the appropriate documentation
- Fixed typo in README-DEV.md ("roote" → "root") for improved clarity
- These changes improve the developer experience by providing better documentation navigation and correcting technical inaccuracies

Author: msanatan

docs/CUSTOM_TOOLS.md

@@ -2,6 +2,11 @@
 
 Unity MCP now supports auto-discovery of custom tools using decorators (Python) and attributes (C#). This allows you to easily extend the MCP server with your own tools without modifying core files.
 
+Be sure to review the developer README first:
+
+| [English](README-DEV.md) | [简体中文](README-DEV-zh.md) |
+|---------------------------|------------------------------|
+
 ## Python Side (MCP Server)
 
 ### Creating a Custom Tool

docs/README-DEV.md

@@ -21,7 +21,7 @@ Quick deployment and testing tools for MCP for Unity core changes.
 
 ## Switching MCP package sources quickly
 
-Run this from the unity-mcp repo, not your game's roote directory. Use `mcp_source.py` to quickly switch between different MCP for Unity package sources:
+Run this from the unity-mcp repo, not your game's root directory. Use `mcp_source.py` to quickly switch between different MCP for Unity package sources:
 
 **Usage:**
 ```bash