vendor: Update PHP Simple HTML DOM Parser to 1.8.1

https://sourceforge.net/projects/simplehtmldom/files/simplehtmldom/1.8.1/

Note: Some bridges may need fixes in their CSS queries if they don't follow
the specification.

lib/rssbridge.php

@@ -65,6 +65,7 @@ require_once PATH_LIB . 'error.php';
 require_once PATH_LIB . 'contents.php';
 
 // Vendor
+define('MAX_FILE_SIZE', 10000000); /* Allow larger files for simple_html_dom */
 require_once PATH_LIB_VENDOR . 'simplehtmldom/simple_html_dom.php';
 require_once PATH_LIB_VENDOR . 'php-urljoin/src/urljoin.php';