Fix plugin parsing

[erri120]

• struct can come after the params declaration and can contain files

/*~struct~Image:
 *
 * @param Id
 * @text Identifier
 * @desc An identifier that uniquely designates a material. If omitted, the file name will become the identifier.
 *
 * @param FilePath
 * @text File Path
 * @desc The file path. Please specify the folder and file.
 * @default
 * @require 1
 * @dir img/
 * @type file
 */