add SMTP mail tester

resources/lang/en/base.php

@@ -86,4 +86,8 @@ return [
         '2fa_checkpoint_help' => 'Use the 2FA application on your phone to take a picture of the QR code to the left, or manually enter the code under it. Once you have done so, generate a token and enter it below.',
         '2fa_disable_error' => 'The 2FA token provided was not valid. Protection has not been disabled for this account.',
     ],
+    'mail' => [
+        'test_succeeded' => 'The test message was sent successfully!',
+        'test_failed' => 'Failed to send test message! Check your configuration and try again.',
+    ],
 ];

resources/themes/pterodactyl/admin/settings/mail.blade.php

@@ -98,7 +98,10 @@
                         </div>
                         <div class="box-footer">
                             {{ csrf_field() }}
-                            <button type="submit" name="_method" value="PATCH" class="btn btn-sm btn-primary pull-right">Save</button>
+                            <div class="pull-right">
+                                <a href="{{ route('admin.settings.mail.test') }}" class="btn btn-sm btn-success">Test</a>
+                                <button type="submit" name="_method" value="PATCH" class="btn btn-sm btn-primary">Save</button>
+                            </div>
                         </div>
                     </form>
                 @endif