[native_assets_cli] Update readme (#1936)

Author: dcharkes

pkgs/native_assets_cli/README.md

@@ -38,10 +38,17 @@ Example can be found in [example/build/](example/build/).
 
 ## Usage
 
-Using the native assets feature requires passing
-`--enable-experiment=native-assets` in Dart on a dev build.
+To use native asset in Dart, pass `--enable-experiment=native-assets`. Native
+assets work on Dart stable, but prefer using the dev releases as we regularly
+break things.
 
-The native assets feature is not yet available in Flutter.
+To use native assets in Flutter, use
+`flutter config --enable-experiment=native-assets` and then
+`flutter create --template=package_ffi <package_name>`. In Flutter, the
+experiment is only available on the master channel.
+
+We do breaking changes regularly! So frequently bump `package:native_assets_cli`
+and use dev/master SDK for CI.
 
 ## Development