django: add download script to file-scrapers.md

docs/file-scrapers.md

@@ -25,8 +25,11 @@ and put it in `/path/to/devdocs/docs/`
 Go to https://docs.djangoproject.com/, select the version from the
 bubble in the bottom-right corner, then download the HTML version from the sidebar.
 
-URL: `https://media.djangoproject.com/docs/django-docs-$VERSION-en.zip`
-
+```sh
+mkdir --parent docs/django\~$VERSION/; \
+curl https://media.djangoproject.com/docs/django-docs-$VERSION-en.zip | \
+bsdtar --extract --file - --directory=docs/django\~$VERSION/
+```
 
 ## Erlang