Add en_GB and en_US

Fixes #210

Author: 2br-2b

src/humanize/i18n.py

@@ -71,6 +71,9 @@ def activate(
     Raises:
         Exception: If humanize cannot find the locale folder.
     """
+    if locale == "en_GB" or locale == "en_US":
+        locale = None
+    
     if path is None:
         path = _get_default_locale_path()