Add deprecation message in shape docs (#1209)

Author: trivikr

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/TypeScriptWriter.java

@@ -190,7 +190,11 @@ boolean writeShapeDocs(Shape shape, UnaryOperator<String> preprocessor) {
                         .replace("}", "\\}");
                     docs = preprocessor.apply(docs);
                     if (shape.getTrait(DeprecatedTrait.class).isPresent()) {
-                        docs = "@deprecated\n\n" + docs;
+                        DeprecatedTrait deprecatedTrait = shape.getTrait(DeprecatedTrait.class).get();
+                        String deprecationMessage = deprecatedTrait.getMessage().orElse("");
+                        String deprecationString = "@deprecated"
+                            + (deprecationMessage.isEmpty() ? "" : " " + deprecationMessage);
+                        docs = deprecationString + "\n\n" + docs;
                     }
                     docs = addReleaseTag(shape, docs);
                     writeDocs(docs);