docs(): add ng-add testing docs to readme (#16478)

angular/README.md

@@ -18,3 +18,38 @@ Ionic Angular specific building blocks on top of [@ionic/core](https://www.npmjs
 ## License
 
 * [MIT](https://raw.githubusercontent.com/ionic-team/ionic/master/LICENSE)
+
+## Testing ng-add in ionic
+
+1. Pull the latest from master
+2. Build ionic/angular: `npm run build`
+3. Run `npm link` from ionic/angular directory
+4. Create a blank angular project
+
+```
+ng new add-test
+// Say yes to including the router, we need it
+cd add-test
+```
+
+5. To run schematics locally, we need the schematics-cli (once published, this will not be needed)
+
+```
+npm install @angular-devkit/schematics-cli
+```
+
+6. Link `@ionic/angular`
+
+```
+npm link @ionic/angular
+```
+
+
+7. Run the local copy of the ng-add schematic
+
+```
+$ npx schematics @ionic/angular:ng-add
+```
+
+
+You'll now be able to add ionic components to a vanilla Angular app setup.