docs(react): adjust Tailwind guide for React

Related issues: #6369

Author: juristr

nx-dev/nx-dev/public/documentation/latest/react/guides/using-tailwind-css-in-react.md

@@ -46,7 +46,11 @@ Nx has a utility function for determining the glob representation of all files t
 const { createGlobPatternsForDependencies } = require('@nrwl/react/tailwind');
 
 module.exports = {
-  purge: createGlobPatternsForDependencies(__dirname),
+  purge: [
+    // place your own app's glob pattern (for example)
+    './apps/{your app here}/src/**/*.{js,ts,jsx,tsx}',
+    ...createGlobPatternsForDependencies(__dirname),
+  ],
   darkMode: false, // or 'media' or 'class'
   theme: {
     extend: {},
@@ -58,6 +62,8 @@ module.exports = {
 };
 ```
 
+`createGlobPatternsForDependencies(..)` uses the Nx dependency graph to generate glob patterns for all the app's **dependencies** (e.g. for all referenced libraries within the Nx workspace).
+
 _NOTE:_ To ensure proper purging for custom configurations, be sure that the `NODE_ENV` environment variable is set to `production`. By default, Nx only purges on prod build (for example: `nx build --prod`).
 
 ## Step 3: Import TailwindCss Styles