feat(config): add Cloudflare R2 filesystem configuration

- Added new environment variables for Cloudflare R2 access key, secret access key, bucket, endpoint, and URL in the .env.example file.
- Updated composer.json to include the league/flysystem-aws-s3-v3 package.
- Modified the filesystems.php configuration file to include a new 'r2' disk for Cloudflare R2 storage.

config/filesystems.php

@@ -44,6 +44,19 @@ return [
             'throw' => false,
         ],
 
+        'r2' => [
+            'driver' => 's3',
+            'key' => env('CLOUDFLARE_R2_ACCESS_KEY_ID'),
+            'secret' => env('CLOUDFLARE_R2_SECRET_ACCESS_KEY'),
+            'region' => 'auto', // != Cloudflare R2 doesn't have specific regions, so 'us-east-1' is fine.
+            'bucket' => env('CLOUDFLARE_R2_BUCKET'),
+            'url' => env('CLOUDFLARE_R2_URL'),
+            'visibility' => 'private',
+            'endpoint' => env('CLOUDFLARE_R2_ENDPOINT'),
+            'use_path_style_endpoint' => env('CLOUDFLARE_R2_USE_PATH_STYLE_ENDPOINT', false),
+            'throw' => false,
+        ],
+
         's3' => [
             'driver' => 's3',
             'key' => env('AWS_ACCESS_KEY_ID'),