Add DocSearch button key theme styles

Introduce .DocSearch-Button-Key styles for light and dark themes: apply text, background, and border colors using Tailwind @apply with important modifiers. The dark variant targets [data-theme="dark"] to ensure search key tokens are visible and consistent across themes.

Author: Deven14125

src/styles/tailwind.css

@@ -47,6 +47,12 @@
 .DocSearch-Button-Keys {
   @apply hidden! lg:flex!;
 }
+.DocSearch-Button-Key {
+  @apply text-gray-700! bg-gray-100! border-gray-300!;
+}
+[data-theme="dark"] .DocSearch-Button-Key {
+  @apply text-gray-100! bg-olive-700! border-gray-500!;
+}
 .DocSearch-Button .DocSearch-Search-Icon {
   @apply text-white! lg:text-gray-100!;
 }