Fix broken link in the README.md (/about.html is now /about/)

README.md

@@ -8,7 +8,7 @@ Take potentially dangerous PDFs, office documents, or images and convert them to
 
 Dangerzone works like this: You give it a document that you don't know if you can trust (for example, an email attachment). Inside of a sandbox, Dangerzone converts the document to a PDF (if it isn't already one), and then converts the PDF into raw pixel data: a huge list of RGB color values for each page. Then, in a separate sandbox, Dangerzone takes this pixel data and converts it back into a PDF.
 
-_Read more about Dangerzone in the [official site](https://dangerzone.rocks/about.html)._
+_Read more about Dangerzone in the [official site](https://dangerzone.rocks/about/)._
 
 ## Getting started