Change how to apply the default namespace

[Tony Lefler]

currently you have to import Scoped and apply your default name as a property on it:

import { Scoped } from 'kremling';
Scoped.defaultNamespace = 'my-default';

I think this would be fine if it only changed the Scoped component, but it also changes useCss...

maybe we introduce a new exported function that sets the default project-wide?

import { setDefaultNamespace } from 'kremling';
setDefaultNameSpace('my-default');