Update 5.3 migration guide

Refs cakephp/cakephp#18703

Author: ADmad

en/appendices/5-3-migration-guide.rst

@@ -58,9 +58,15 @@ Console
 Database
 --------
 
-- Added ``Query::getDriver()`` helper which returns the ``Driver`` for the current connection 
+- Added ``Query::getDriver()`` helper which returns the ``Driver`` for the current connection
   role by default.
 
+Mailer
+------
+
+- Added ``Message::addAttachment()`` for adding attachments to a message. Like
+  other message methods, it can be accessed via the ``Mailer`` instance as ``$mailer->addAttachment()``.
+
 Routing
 -------
 

en/core-libraries/email.rst

@@ -278,6 +278,12 @@ you want the filenames to appear in the recipient's mail client:
    a string using the ``data`` option. This allows you to attach files without
    needing file paths to them.
 
+.. php:method:: addAttachment(\Psr\Http\Message\UploadedFileInterface|string $path, ?string $name, ?string $mimetype, ?string $contentId, ?bool $contentDisposition)
+
+You can also add attachments using the ``addAttachment()`` method.
+
+    $mailer->addAttachment('/full/file/path/file.png');
+
 Relaxing Address Validation Rules
 ---------------------------------