message: fix typo in The App Frontend learning article
diff: @@ -4,9 +4,9 @@ The frontend of an app refers to the layers of software that are concerned mainl
  The frontend *always* runs inside a web browser.
  -* When used with a backend service via HTTP, it can run in any modern web browser (see compatibility list.)
  -* When used with a desktop apps, it runs inside the Electron frontend process in Chrome.
  -* When used in a mobile app, it runs inside the Safari built-in browser on iOS and the Chrome browser for Android.
  +* When used as a Web app, it can run in any modern web browser. See compatibility list. It communicates with a backend and/or other services via HTTP.
  +* When part of a desktop app, it runs inside the Electron frontend process in Chrome.
  +* When part of a mobile app, it runs inside the Safari built-in browser on iOS and the Chrome browser for Android.
  An app always implements its own frontend script and resources. The app's frontend script must depend on @bentley/imodeljs-frontend.
  