docs: add contentType to openapi-generator README

Author: koralkulacoglu

packages/openapi-generator/README.md

@@ -468,6 +468,8 @@ const SampleSchema = t.type({
 
 These are some tags that you can use in your schema JSDocs are custom to this generator.
 
+- `@contentType` allows you to override the default `application/json` content type for
+  requests and responses. Can be applied at route, request body, or response body level.
 - `@private` allows you to mark any field as in any schema as private. The final spec
   will have `x-internal: true` for schemas with the `@private` tag.
 - `@deprecated` allows to mark any field in any schema as deprecated. The final spec
@@ -477,6 +479,8 @@ These are some tags that you can use in your schema JSDocs are custom to this ge
 import * as t from 'io-ts';
 
 const Schema = t.type({
+  /** @contentType application/xml */
+  xmlField: t.string,
   /** @private */
   privateField: t.string,
   /** @deprecated */