fix parsing of `PropType` types in storybook Prop table tab

[williaster]

all data-ui + vx proptypes show as other in the storybook:

this likely has to do with prop type functions being stripped during babel parsing / some build issue. may need to restructure the repo to fix it. may not be fixable for @vx issues

[williaster]

Going to punt on this until Storybook updates are out!