update README to include the new Assess (-a) feature in the CLI.

README.org

@@ -240,6 +240,11 @@ program. You don't need to touch this part.
   # program looks for. If you do use a custom path, you will to use -c whenever
   # you run this program.
   ./dup -m ~/ddns-updater.json
+  # To validate the schema of your config. file. Note, this only checks to make
+  # sure your config. file has the correct ‘keys’ in it. Your access tokens and
+  # Id’s are not validated. Incorrect access token and Id’s will produce and error
+  # messges stating which ones are wrong when you try and use the program, though.
+  ./dup -a <PATH TO YOUR DDNS-UPDATER.JSON FILE>
   # Run the program in 'verbose' mode.
   ./dup -v
 #+end_src