[url_launcher] Added a note to the README (#2031)

The action won't work on the simulator works on physical iOS device which was not mentioned here so it was added

Co-authored-by: Michael Klimushyn <mklim@google.com>
Co-authored-by: Stuart Morgan <stuartmorgan@google.com>
diff --git a/packages/url_launcher/url_launcher/CHANGELOG.md b/packages/url_launcher/url_launcher/CHANGELOG.md
index 01f3e78..2d18836 100644
--- a/packages/url_launcher/url_launcher/CHANGELOG.md
+++ b/packages/url_launcher/url_launcher/CHANGELOG.md
@@ -1,6 +1,7 @@
 ## 6.0.1
 
 * Update result to `True` on iOS when the url was loaded successfully.
+* Added a README note about required applications.
 
 ## 6.0.0
 
diff --git a/packages/url_launcher/url_launcher/README.md b/packages/url_launcher/url_launcher/README.md
index bc399c7..daf2173 100644
--- a/packages/url_launcher/url_launcher/README.md
+++ b/packages/url_launcher/url_launcher/README.md
@@ -51,6 +51,10 @@
 
 More details can be found here for [iOS](https://developer.apple.com/library/content/featuredarticles/iPhoneURLScheme_Reference/Introduction/Introduction.html) and [Android](https://developer.android.com/guide/components/intents-common.html)
 
+**Note**: URL schemes are only supported if there are apps installed on the device that can
+support them. For example, iOS simulators don't have a default email or phone
+apps installed, so can't open `tel:` or `mailto:` links.
+
 ### Encoding URLs
 
 URLs must be properly encoded, especially when including spaces or other special characters. This can be done using the [`Uri` class](https://api.dart.dev/stable/2.7.1/dart-core/Uri-class.html):