build: enable namespace verification for default theme
Summary:
this will trigger a build failure if someone modifies the theme in such
a way that namespacing is not used correctly, saving some time when
reviewing larger patches which have many theme changes
Reviewers: cedric
Reviewed By: cedric
Subscribers: committers
Tags: efl
Maniphest Tasks: T6911
Differential Revision: https://phab.enlightenment.org/D6042