adds px-expect function to override utility suite

packages/formation/sass/override-function.scss

@@ -154,4 +154,13 @@ $unit-types: (
     $scaled: append($scaled, $scaled-value, $separator);
   }
   @return $scaled;
-}
+}
+
+// returns the rem value equivalent to expected px 
+// for uswds, [optional:true], returns same for formation
+@function px-expect($exp, $to-formation : false) {
+  $denom : if($to-formation, $uswds-base, $formation-base);
+  $coeff : if($to-formation, $u2f-coeff, $f2u-coeff);
+  $exp: $exp * 1px;
+  @return  ($exp/$denom)  *  $coeff + rem;
+ }