Document, add to changelog the data migrations and rename to 'warnings-as-errors' (plural)

docs/usage.md

@@ -25,6 +25,7 @@ Detailed command line options:
 |`--project-root-path DJANGO_PROJECT_FOLDER`                   | An absolute or relative path to the django project.                                                                         |
 |`--include-migrations-from FILE_PATH`                         | If specified, only migrations listed in the given file will be considered.                                                  |
 |`--quiet or -q {ok,ignore,warning,error}`                     | Suppress certain output messages, instead of writing them to stdout.                                                        |
+|`--warnings-as-errors`                                        | Handle warnings as errors and therefore return an error status code if we should.                                           |
 
 ## Ignoring migration tests