updated README about HTTP CORS [skip ci]

Author: danielweck

README.md

@@ -76,7 +76,13 @@ The above task takes a lot of time (as it builds distributable packages for *all
 Remember to activate "developer mode" in the Chrome web browser, so that the Readium packaged app / extension can be added directly from the `dist/chrome-app` folder. Subsequently (after each build), the app can simply be reloaded.
 
 
-Also note that the built-in local HTTP server functionality (`npm run http`) is primarily designed to serve the Readium application at development time in its "exploded" form (`dev`, `src`, `node_modules`, etc. folders). However, it is also possible to use any arbitrary HTTP server as long as the root folder is `readium-js-viewer` (so that the application assets ; CSS, images, fonts ; can be loaded relative to this base URL). Example with the built-in NodeJS server: `node node_modules/http-server/bin/http-server -a 127.0.0.1 -p 8080 -c-1 .` (unlike `npm run http`, this completely bypasses the HTTP CORS configuration which separates app vs. ebooks into distinct domains / origins).
+Also note that the built-in local HTTP server functionality (`npm run http`) is primarily designed to serve the Readium application at development time in its "exploded" form (`dev`, `src`, `node_modules`, etc. folders). However, it is also possible to use any arbitrary HTTP server as long as the root folder is `readium-js-viewer` (so that the application assets ; CSS, images, fonts ; can be loaded relative to this base URL). Example with the built-in NodeJS server: `node node_modules/http-server/bin/http-server -a 127.0.0.1 -p 8080 -c-1 .`
+
+
+### HTTP CORS (separate domains / origins, app vs. ebooks)
+
+By default, a single HTTP server is launched when using the `npm run http` task, or its "watch" and "nowatch" variants (usage described in the above "Typical workflow" section).
+To launch separate local HTTP servers on two different domains (in order to test HTTP CORS cross-origin app vs. ebooks deployment architecture), simply invoke the equivalent tasks named with `http2` instead of `http`. For example: `npm run http2`. More information about real-world HTTP CORS is given in the "Cloud reader deployment" section below.
 
 ### Forking