feat(Separator): new component (#46)

Co-authored-by: Benjamin Canac <canacb1@gmail.com>

src/theme/index.ts

@@ -17,6 +17,7 @@ export { default as modal } from './modal'
 export { default as navigationMenu } from './navigation-menu'
 export { default as popover } from './popover'
 export { default as radioGroup } from './radio-group'
+export { default as separator } from './separator'
 export { default as skeleton } from './skeleton'
 export { default as slideover } from './slideover'
 export { default as switch } from './switch'