Update README.md

Co-authored-by: Kevin Paul <kpaul@ucar.edu>

Author: clyne

README.md

@@ -45,7 +45,7 @@ However, many of the links will not work. For all of the links found in the port
 python -m http.server --directory _build/html/
 ```
 
-and then pointing your browser at the URL: `localhost:8000`
+and then pointing your browser at the URL: `localhost:8000`.
 
 More information on setting up a local test server is available from [here](https://developer.mozilla.org/en-US/docs/Learn/Common_questions/set_up_a_local_testing_server)