Updated the readme with src/etc build info

README.md

@@ -6,6 +6,19 @@ CDN URL: https://npm-cdn.com/pkg/aria-query/
 
 Programmatic access to the [WAI-ARIA 1.1 Roles Model](https://www.w3.org/TR/wai-aria-1.1/#roles).
 
+## Building the `src/etc` files.
+
+The files under `src/etc` are generated by the `breakUpAriaJSON` script. 
+
+To change them, edit the file `scripts/roles.json` then run:
+
+```
+$ node ./scripts/breakUpAriaJSON.js
+$ git add scripts/roles.json src/etc
+```
+
+It should work with Node version 6.11.2 or later.
+
 ## Utilities
 
 ### Roles