Fix decode filename (#535)

Author: grnsv

src/Attachment.php

@@ -307,6 +307,7 @@ public function decodeName(?string $name): string {
  if (str_contains($name, "''")) {
  $parts = explode("''", $name);
  if (EncodingAliases::has($parts[0])) {
+ $encoding = $parts[0];
  $name = implode("''", array_slice($parts, 1));
  }
  }
@@ -323,6 +324,10 @@ public function decodeName(?string $name): string {
  $name = urldecode($name);
  }
 
+ if (isset($encoding)) {
+ $name = EncodingAliases::convert($name, $encoding);
+ }
+
  // sanitize $name
  $replaces = [
  '/\\\\/' => '',