style(doc): tweak the icon color on the homepage

layouts/partials/contributors.html

@@ -2,7 +2,7 @@
 <section class="contributors-section mt-12 mb-16">
   <div class="flex flex-col items-center mb-6">
     <div class="flex items-center gap-2 mb-2">
-      <span class="text-2xl text-neutral-600 dark:text-neutral-400">
+      <span class="text-2xl text-neutral-800 dark:text-neutral-200">
         {{ partial "icon.html" "github" }}
       </span>
       <h2 class="text-2xl font-extrabold text-neutral-800 dark:text-neutral-200">