Update release notes for 0.4.0

Author: mbeissinger

RELEASE.md

@@ -1,3 +1,10 @@
+# Release 0.4.0
+___
+## Bug Fixes and Other Improvements
+* Fix API return signature for Lobe 0.9
+* Make backwards-compatible with earlier versions of model exports
+
+
 # Release 0.3.0
 ___
 ## Breaking Changes
@@ -9,4 +16,4 @@ ___
 * Add ONNX runtime backend
 * Use requests instead of urllib
 * Make backends thread-safe
-* Added constants file for signature keys to enable backwards-compatibility
+* Added constants file for signature keys to enable backwards-compatibility