docs: fix brick description (#8)

Author: felangel

brick.yaml

@@ -1,5 +1,5 @@
 name: flutter_web_preloader
-description: A brick that creates a smart web entry point for Flutter that preloads its assets before starting the app;
+description: A brick that creates a smart web entry point for Flutter that preloads its assets before starting the app.
 repository: https://github.com/VeryGoodOpenSource/flutter_web_preloader
 version: 0.1.0