Support outputting closed ATX headers in Markdown output

[mcdonnnj]

What problem are you facing?

My team prefers to format our Markdown documents with closed ATX headers. As a result, when using injection with terraform-docs the headers conflict with our preferred style.

How could terraform-docs help solve your problem?

Since terraform-docs already outputs Markdown documents with open ATX headers, if there was an option to close them it would resolve this issue completely.