Clarify params

src/PHPMailer.php

@@ -3313,15 +3313,16 @@ public function addEmbeddedImage($path, $cid, $name = '', $encoding = 'base64',
     /**
      * Add an embedded stringified attachment.
      * This can include images, sounds, and just about any other document type.
-     * Be sure to set the $type to an image type for images:
-     * JPEG images use 'image/jpeg', GIF uses 'image/gif', PNG uses 'image/png'.
+     * If your filename doesn't contain an extension, be sure to set the $type to an appropriate MIME type.
      *
      * @param string $string      The attachment binary data
      * @param string $cid         Content ID of the attachment; Use this to reference
      *                            the content when using an embedded image in HTML
-     * @param string $name
-     * @param string $encoding    File encoding (see $Encoding)
-     * @param string $type        MIME type
+     * @param string $name        A filename for the attachment. If this contains an extension,
+     *                            PHPMailer will attempt to set a MIME type for the attachment.
+     *                            For example 'file.jpg' would get an 'image/jpeg' MIME type.
+     * @param string $encoding    File encoding (see $Encoding), defaults to 'base64'
+     * @param string $type        MIME type - will be used in preference to any automatically derived type
      * @param string $disposition Disposition to use
      *
      * @return bool True on successfully adding an attachment