Show description when summary is missing (OpenAPITools#6159)

Author: ybelenko

modules/openapi-generator/src/main/resources/markdown-documentation/README.mustache

@@ -8,7 +8,7 @@ All URIs are relative to *{{{basePath}}}*
 
 Class | Method | HTTP request | Description
 ------------ | ------------- | ------------- | -------------
-{{#apiInfo}}{{#apis}}{{#operations}}{{#operation}}*{{classname}}* | [**{{operationId}}**](Apis/{{apiDocPath}}{{classname}}.md#{{operationIdLowerCase}}) | **{{httpMethod}}** {{path}} | {{#summary}}{{{summary}}}{{/summary}}
+{{#apiInfo}}{{#apis}}{{#operations}}{{#operation}}*{{classname}}* | [**{{operationId}}**](Apis/{{apiDocPath}}{{classname}}.md#{{operationIdLowerCase}}) | **{{httpMethod}}** {{path}} | {{#summary}}{{{summary}}}{{/summary}}{{^summary}}{{{notes}}}{{/summary}}
 {{/operation}}{{/operations}}{{/apis}}{{/apiInfo}}
 {{/generateApiDocs}}