chore: add favicon to WDS Storybook (#26567)

tl;dr there was no favicon, added one. Slightly different fills for
light and dark mode.

---------

Co-authored-by: Valera Melnikov <valera@appsmith.com>

app/client/packages/storybook/.storybook/manager-head.html

@@ -2,7 +2,10 @@
   img[alt="Appsmith Design System"] {
     width: 134px;
   }
-  #storybook-explorer-tree > div {
+
+  #storybook-explorer-tree>div {
     margin: unset !important;
   }
 </style>
+
+<link rel="icon" type="image/svg+xml" href="/favicon.svg" sizes="any">

app/client/packages/storybook/public/favicon.svg

@@ -0,0 +1,14 @@
+<svg xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 16 16">
+  <style>
+    .bg {
+    fill: #542bd1;
+    }
+    @media (prefers-color-scheme: dark) {
+    .bg {
+    fill: #734bee;
+    }
+    }
+  </style>
+  <path class="bg" d="M0 0h16v16H0z" />
+  <path fill="#fff" d="M3 13v-2h10v2H3Z" />
+</svg>