configitems: fix registration of extensions config
The new 'itemregister' class should be used when loading the extension config.
This was and oversight when itemregister was introduced.
# See http://EditorConfig.org for the specification
root = true
[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true
[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true