Add note about adult sites.

CONTRIBUTING.md

@@ -13,6 +13,11 @@ Any new sites that are added need to have a username that has been claimed, and
 that is unclaimed documented in the site data.  This allows the regression tests
 to ensure that everything is working.
 
+In regards to adult sites (e.g. PornHub), we have agreed to not include them in Sherlock.  
+However, we do understand that some users desires this support.  The data.json file is easy to add to, 
+so users will be able to maintain their own forks to have this support. This is not ideal.  
+Maybe there could be another repo with an adult data.json? That would avoid forks getting out of date.
+
 ## Adding New Functionality
 
 Please ensure that the content on your branch passes all tests before submitting a pull request.