Add dc terms subject keywords

https://www.dublincore.org/specifications/dublin-core/dcmi-terms/#http://purl.org/dc/elements/1.1/subject

Author: abetwothree

src/Detectors/Keywords.php

@@ -18,6 +18,7 @@ public function detect(): array
             'og:video:tag',
             'og:book:tag',
             'lp.article:section',
+            'dcterms.subject',
         ];
 
         foreach ($types as $type) {