Nord Snow Storm: lighten code chunk background

src/nord-snow-storm.scss

 // primary UI colors
 $ui-background           : lighten($nord6, 10%);
 $ui-foreground           : $nord3;
-$ui-code-chunk-background: $nord6;
+$ui-code-chunk-background: transparentize($nord6, 0.5);
 $ui-selection            : transparentize($nord4, 0.6);
 $ui-cursor               : $nord12;
 $ui-cursor-normal-mode   : $ui-cursor;
 $ui-completions-color           : $ui-foreground;
 $ui-completions-border          : $ui-bracket;
 $ui-rstudio-scrollbar-background: $ui-background;
-$ui-rstudio-scrollbar-handle    : $ui-code-chunk-background;
+$ui-rstudio-scrollbar-handle    : $nord6;
 
 // R language colors
 $rlang-comment  : transparentize($ui-foreground, 0.5);