Add changelog

Author: alextwoods

.changes/next-release/feature-AWSSDKforJavav2-838b5da.json

@@ -0,0 +1,6 @@
+{
+    "type": "feature",
+    "category": "AWS SDK for Java v2",
+    "contributor": "",
+    "description": "Convert codegen exceptions caused by bad customization config or invalid models to ModelInvalidException."
+}