New lines in description create incorrect markdown

## Problem statement

Converting a swagger.yaml file to swagger.md create incorrect markdown, because the new lines are not remove/escaped (or what ever is needed).

https://github.com/argoproj/argo-workflows/issues/7615

## Swagger specification

## Steps to reproduce

## Environment
swagger version: v0.29.0
go version: 1.17
OS:   MacOS
