I am currently writing a Google Chrome Extension that you can use to highlight keywords on any page. The idea is that you open a page, click a button and certain words are highlighted, counted, and put into some type of chart. I am not sure how to go about doing this. The thought was to scrape the page of the article, scan the article, and produce a mask with highlights (if this is even possible). I know there are options out there that will allow me to scrape content from a page, but Google Chrome Extensions don't allow for a lot of inclusion of outside libraries (maybe I'm wrong on this) unless you can have some type of offline version. Can someone please point me in the right direction on where to start with this particular task, if it is possible?

Thanks in advance!