Add Id to header

[pappou99]

Problem
I'm including markdown files into LaTeX, which I generate with mdutils.
Before I can do this I have to slice some sections, which I don't want to include. This can only be done by named Id's.
Id's are described in Extended Markdown Sythax

Describe the solution you'd like
Please add an option to add an id to a new header like:

MdUtils.new_header(level=3, title="My Great Heading", id="greatheader")

so it returns:

### My Great Heading {#greatheader}

or so