update README with enableJavaScript info (flutter#2766)

Author: cg021

packages/url_launcher/url_launcher/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 5.4.9
+
+* Update README.
+
 ## 5.4.8
 
 * Initialize `previousAutomaticSystemUiAdjustment` in launch method.

packages/url_launcher/url_launcher/README.md

@@ -70,6 +70,8 @@ web page using a URL following the `http` scheme.
 
 ## Browser vs In-app Handling
 By default, Android opens up a browser when handling URLs. You can pass
-forceWebView: true parameter to tell the plugin to open a WebView instead. On
+`forceWebView: true` parameter to tell the plugin to open a WebView instead. 
+If you do this for a URL of a page containing JavaScript, make sure to pass in 
+`enableJavaScript: true`, or else the launch method will not work properly. On
 iOS, the default behavior is to open all web URLs within the app. Everything
 else is redirected to the app handler.

packages/url_launcher/url_launcher/pubspec.yaml

@@ -2,7 +2,7 @@ name: url_launcher
 description: Flutter plugin for launching a URL on Android and iOS. Supports
   web, phone, SMS, and email schemes.
 homepage: https://github.com/flutter/plugins/tree/master/packages/url_launcher/url_launcher
-version: 5.4.8
+version: 5.4.9
 
 flutter:
   plugin: