docs(README): update coverage badge and minor copy

- Change test coverage badge to display blank (%) value
- Refine product description to mention mobile client specifically

Author: fulleni

README.md

@@ -7,14 +7,14 @@
 <p align="center">
   <a href="https://flutter-news-app-full-source-code.github.io/flutter-news-app-mobile-client-full-source-code/"><img src="https://img.shields.io/badge/LIVE_DEMO-VIEW-orange?style=for-the-badge" alt="Live Demo: View"></a>
   <a href="https://flutter-news-app-full-source-code.github.io/docs/mobile-client/local-setup/"><img src="https://img.shields.io/badge/DOCUMENTATION-READ-slategray?style=for-the-badge" alt="Documentation: Read"></a>
-  <img src="https://img.shields.io/badge/coverage-XX%25-green?style=for-the-badge" alt="coverage: XX%">
+  <img src="https://img.shields.io/badge/coverage-_%25-green?style=for-the-badge" alt="coverage: _%">
 </p>
 <p align="center">
   <a href="LICENSE"><img src="https://img.shields.io/badge/TRIAL_LICENSE-VIEW_TERMS-blue?style=for-the-badge" alt="Trial License: View Terms"></a>
   <a href="https://github.com/sponsors/flutter-news-app-full-source-code"><img src="https://img.shields.io/badge/LIFETIME_LICENSE-PURCHASE-purple?style=for-the-badge" alt="Lifetime License: Purchase"></a>
 </p>
 
-This repository contains the complete, production-ready source code for a feature-rich Flutter news mobile app. It gives you everything you need to launch your own news app on the App Store and Google Play, right out of the box. It is a key component of the [**Flutter News App Full Source Code Toolkit**](https://github.com/flutter-news-app-full-source-code), an ecosystem that also includes a Dart Frog [backend API](https://github.com/flutter-news-app-full-source-code/flutter-news-app-api-server-full-source-code) and a web-based [content dashboard](https://github.com/flutter-news-app-full-source-code/flutter-news-app-web-dashboard-full-source-code).
+This repository contains the complete, production-ready source code for a feature-rich Flutter news app mobile client. It gives you everything you need to launch your own news app on the App Store and Google Play, right out of the box. It is a key component of the [**Flutter News App Full Source Code Toolkit**](https://github.com/flutter-news-app-full-source-code), an ecosystem that also includes a Dart Frog [backend API](https://github.com/flutter-news-app-full-source-code/flutter-news-app-api-server-full-source-code) and a web-based [content dashboard](https://github.com/flutter-news-app-full-source-code/flutter-news-app-web-dashboard-full-source-code).
 
 ## ⭐ Feature Showcase: Everything You Get, Ready to Go