Bug in generating markdown files with characters *(){}[]-

[manlopes]

Hi, I've noticed that, when generating markdown files with some characters like "*(){}[]-", the output is not correct and backslashes are added to the md file before each of the characters. See example below:

Source comment:

// **param** c (context.Context): Execution context

markdown output

\*\*param\*\* ctx \(context.Context\): Execution context

This issue is similar to issue https://github.com/princjef/gomarkdoc/issues/68