added some notes about building to the root readme

Author: bennage

README.md

@@ -3,6 +3,18 @@ Microsoft patterns & practices
 
 http://aka.ms/architecture
 
+## Understanding the local build process
+
+Some of the markdown files are generated from data stored in json files.
+This is primarily to avoid human error for pages that still require some HTML.
+The process that converts the json to markdown uses a utility script located in the `build` folder.
+To run the build script, navigate to the root folder of this repository.
+
+```bash
+npm install
+node .\build\build.js
+```
+
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