Add language-data updating instructions to README

README.md

@@ -123,6 +123,15 @@ To run tests locally, run `grunt test`. This will run the tests in PhantomJS.
 
 You can also run the tests in a browser by navigating to the `test/` directory, but first run `grunt` to install the submodules.
 
+Updating language-data
+----------------------------------
+
+From the main repo directory, run:
+
+```shell
+./scripts/fetch-language-data.sh
+```
+
 Coding style
 -------------