Switch to predominant use of appDescriptionWithNewLines in README.mustache
Descriptions tend to get lengthy and can include multiple lines.
New lines are important to markdown formatting/syntax and can't just be ignored.
Resolves
# Go API client for {{packageName}}
-{{#appDescription}}
-{{{appDescription}}}
-{{/appDescription}}
+{{#appDescriptionWithNewLines}}
+{{{appDescriptionWithNewLines}}}
+{{/appDescriptionWithNewLines}}
## Overview
This API client was generated by the [OpenAPI Generator](https://openapi-generator.tech) project. By using the [OpenAPI-spec](https://www.openapis.org/) from a remote server, you can easily generate an API client.
