API: add method to get the HTML (parts) instead of always saving and showing it

[johann-petrak]

This would be useful in all contexts where the library is used in a context which already shows HTML, e.g. Jupyter notebooks, dash, etc.

What is really needed is to retrieve the generated div for the report plus the necessary javascript and styling. Depending on how the HTML output is designed, it may be sufficient to include javascript and styling only once in each page.

I did not look at the generated HTML in detail, but for this to work it would also be useful if all HTML classes would have a choosable prefix and any ids that are used for one report are generated so that they do not clash with any other report embedded in the same HTML.

[fbdesignpro]

@johann-petrak thank you for the feedback; exactly what you described is a top priority of mine for the next major update, it will just be a matter of finding the time, but it will happen.

I am actually looking into doing a more "vertical" layout because notebooks seem to be more "thin". There IS a way to make the output wider (i.e. Take up the full screen width instead of just the middle part) but I'm not sure if notebook users would be happy if the system messed with their setup.