Update README.md

Make link more accurate

README.md

@@ -107,7 +107,7 @@ Just some examples
     json://someserver.com/custom-api
     syslog://
  
-<a href="https://github.com/caronc/apprise">And everything else in this list!</a>
+<a href="https://github.com/caronc/apprise#popular-notification-services">And everything else in this list!</a>
 
 <img src="https://raw.githubusercontent.com/dgtlmoon/changedetection.io/master/screenshot-notifications.png" style="max-width:100%;" alt="Self-hosted web page change monitoring notifications"  title="Self-hosted web page change monitoring notifications"  />