Fix one error regarding xml code inside html

Dear matiskay,

I am using your library to compare http and https Portuguese websites. Some of the websites still use XML inside HTML. I added one condition to your code to support lxml.html.HtmlProcessingInstruction (the XML tags were as the previously mentioned class). Can you add this fix to your code?

Thanks, Catarina

Hi @catarinaacsilva, sorry I miss this. I will test this out later today. Thanks

Hi @catarinaacsilva thanks for the effort on adding feature. I'm working on a new version of the package and I will include fix into it. stay tune.

@matiskay Just out of curiousity, is this sitll an active project? (Also, thank you for your great work)

@matiskay Thanks for your work. I am also using this package and was wondering if the project is still active.