make imgs easier on the eyes in dark mode

input.css

···
             @apply no-underline text-black hover:underline hover:text-gray-800 dark:text-white dark:hover:text-gray-300;
         }
 
+        img {
+            @apply dark:brightness-75 dark:opacity-90;
+        }
+
         label {
             @apply block mb-2 text-gray-900 text-sm font-bold py-2 uppercase dark:text-gray-100;
         }