feat(atoms): add overflow_visible utility

Added the `overflow_visible` atom to the atoms utility object for
setting CSS overflow to 'visible'. This complements the existing
`overflow_hidden` atom and improves flexibility for layout styling.

src/alf/atoms.ts

@@ -67,6 +67,9 @@ export const atoms = {
     zIndex: 50,
   },
 
+  overflow_visible: {
+    overflow: 'visible',
+  },
   overflow_hidden: {
     overflow: 'hidden',
   },