includes gettext portable and machine objects in Python package

After #1348, setuptools is not responsible for compiling the portable to
machine objects, only for including both as produced by Weblate.

setup.py

@@ -35,4 +35,5 @@
         "Operating System :: OS Independent",
     ],
     entry_points={"console_scripts": ["sd-client = securedrop_client.app:run"]},
+    package_data={"": ["locale/*/*/*.mo", "locale/*/*/*.po"]},
 )