Compatibility with other customizable markdown standards

[WalissonRodrigo]

I am integrating slack via webhooks into my react application however slack partially uses markdown when I have formatting in the text content. So bold, italic, underline, etc ... need styles different from the standard generated by the library in version 0.6.0. As I needed to solve my problem I thought about sharing my solution in the main project.

Basically the previous version is not affected and nothing is completely changed, not by my local tests. So whoever needs to integrate a Slack of life like me can change the properties they want generating a final text that is very consistent with what their integration expects.

Another problem was the line break that was not included in the string itself and that in my integration it was necessary to render the text breaks correctly.