refactor: improve drag thumb styles

Author: nzbin

projects/color-picker/src/lib/color-alpha-slider.scss

@@ -32,5 +32,5 @@
   transform: translate(-50%,
       calc((var(--cp-slider-thumb-height, 12px) - var(--cp-slider-height, 10px)) / -2));
   background-color: var(--cp-slider-thumb-background-color, #f8f8f8);
-  box-shadow: var(--cp-slider-thumb-shadow, 0 1px 4px 0 rgba(0, 0, 0, 0.32));
+  box-shadow: var(--cp-slider-thumb-shadow, 0 1px 4px 0 rgba(0, 0, 0, 0.32), 0 2px 8px 0 rgba(0, 0, 0, 0.16));
 }

projects/color-picker/src/lib/color-hue-slider.scss

@@ -24,7 +24,7 @@
   transform: translate(-50%,
       calc((var(--cp-slider-thumb-height, 12px) - var(--cp-slider-height, 10px)) / -2));
   background-color: var(--cp-slider-thumb-background-color, #f2f2f2);
-  box-shadow: var(--cp-slider-thumb-shadow, 0 1px 4px 0 rgba(0, 0, 0, 0.32));
+  box-shadow: var(--cp-slider-thumb-shadow, 0 1px 4px 0 rgba(0, 0, 0, 0.32), 0 2px 8px 0 rgba(0, 0, 0, 0.16));
 }
 
 .color-hue-horizontal {

projects/color-picker/src/lib/color-saturation-picker.scss

@@ -30,4 +30,5 @@
   outline: 1px solid #fff;
   outline-offset: -1px;
   transform: translate(-50%, -50%);
+  box-shadow: 0 2px 6px 0 rgba(0, 0, 0, 0.32);
 }