Update the back component to show white text if dark theme is turn on.

lib/decentralised_book_index_web/components/core_components.ex

@@ -624,7 +624,7 @@ defmodule DecentralisedBookIndexWeb.CoreComponents do
     <div class="mt-16">
       <.link
         navigate={@navigate}
-        class="text-sm font-semibold leading-6 text-zinc-900 hover:text-zinc-700"
+        class="text-sm font-semibold leading-6 text-zinc-900 hover:text-zinc-700 dark:text-white dark:hover:text-white/70"
       >
         <.icon name="hero-arrow-left-solid" class="h-3 w-3" />
         {render_slot(@inner_block)}