README.md in dockly-2.1.0 vs README.md in dockly-2.2.0

@@ -109,9 +109,12 @@
 
 - `registry_import`
     - required: `false` -- only required when `import` is not supplied
     - description: the location  of the base image to start building from
     - examples: `paintedfox/ruby`, `registry.example.com/my-custom-image`
+- `build_env`
+    - required: `false`
+    - description: Hash whose values are environment variables and keys are their values. These variables are only used during build commands, exported images will not contain them.
 - `import`
     - required: `false` -- only required when `registry_import` is not supplied
     - description: the location (url or S3 path) of the base image to start building from
 - `git_archive`:
     - required: `false`