adds an example of a boolean knob
adds an example of a boolean knob

proves that the boolean knob works as expected
storybooks/react-storybook,storybooks/storybook,kadirahq/react-storybook,kadirahq/react-storybook,storybooks/storybook,storybooks/storybook,storybooks/react-storybook,storybooks/storybook,storybooks/storybook,storybooks/react-storybook,storybooks/storybook,storybooks/react-storybook,storybooks/storybook