improve: enhance contributors loading state accessibility and feedback (JhaSourav07#2056)

## Summary

This PR improves the Contributors page loading experience by enhancing
the existing loading state with better accessibility support and
additional user feedback.

## Changes Made

* Added `role="status"` to improve screen reader support.
* Added `aria-live="polite"` to announce loading updates to assistive
technologies.
* Added a visually hidden (`sr-only`) loading message for accessibility.
* Added an additional helper message informing users that contributor
data is being fetched from GitHub.
* Preserved the existing loading spinner and functionality.

## Benefits

* Improves accessibility for users relying on screen readers.
* Provides clearer feedback while contributor data is loading.
* Enhances the overall user experience during network requests.
* Makes the loading state more informative and user-friendly.

## Testing

* Verified that the loading screen renders correctly.
* Verified that the spinner animation remains unchanged.
* Verified that additional loading messages are displayed properly.
* Confirmed that contributor data loads as expected once fetching is
complete.

Closes JhaSourav07#2010

Author: JhaSourav07

app/contributors/loading.tsx

@@ -1,9 +1,14 @@
 export default function Loading() {
   return (
-    <div className="flex min-h-screen items-center justify-center bg-white text-black dark:bg-black dark:text-white transition-colors">
-      <div className="flex flex-col items-center gap-4">
+    <div className="flex min-h-screen items-center justify-center bg-white text-black transition-colors dark:bg-black dark:text-white">
+      <div className="flex flex-col items-center gap-4" role="status" aria-live="polite">
         <div className="h-14 w-14 animate-spin rounded-full border-4 border-cyan-400 border-t-transparent" />
-        <p className="text-zinc-500 dark:text-zinc-400">Loading contributors...</p>{' '}
+
+        <p className="text-zinc-500 dark:text-zinc-400">Loading contributors...</p>
+
+        <p className="text-sm text-zinc-400 dark:text-zinc-500">
+          Fetching contributor data from GitHub
+        </p>
       </div>
     </div>
   );