add gentle anim

Author: mayank1513

lib/nthul/src/styles.css

@@ -26,14 +26,28 @@
   content: "A";
 }
 
+.light.nthul--color-switch {
+  box-shadow: 0 0 50px 10px yellow;
+  background-color: yellow;
+  border: 1px solid orangered;
+}
+
 .dark.nthul--color-switch {
   box-shadow: calc(var(--size) / 4) calc(var(--size) / -4) calc(var(--size) / 8) inset #fff;
   border: none;
   background: transparent;
+  animation: swing linear 0.5s;
 }
 
-.light.nthul--color-switch {
-  box-shadow: 0 0 50px 10px yellow;
-  background-color: yellow;
-  border: 1px solid orangered;
+@keyframes swing {
+  40% {
+    transform: rotate(-15deg);
+  }
+  80% {
+    transform: rotate(10deg);
+  }
+  0%,
+  100% {
+    transform: rotate(0deg);
+  }
 }