:bug: Blank lines in docstrings have spaces added

[jgopel]

Problem:

• reformat-gherkin should strip all trailing spaces from docstrings. It currently adds spaces to blank lines in docstrings

Solution:

• Only output indent if the line is non-empty.

Please delete options that are not relevant.

• [ ] Bug fix (non-breaking change which fixes an issue)

[ducminh-phan]

@jgopel Thank you for your contribution!