Styles used to format of generated documents should be configurable

[it-praktyk]

Currently styles used to format documents are hardcoded in Format-Pester.ps1 e.g. https://github.com/equelin/Format-Pester/blob/master/Format-Pester/Public/Format-Pester.ps1#L257-L261

Styles used to format of generated documents should be configurable e.g. via style files / templates.

@iainbrighton , do you have idea how it can be done correctly?

[it-praktyk]

The related issue: iainbrighton/PScribo#43