change template to authors to accomodate author taxonomy

lumbunglib/templates/feed.md

@@ -3,7 +3,7 @@ title: "{{ frontmatter.title }}"
 date: "{{ frontmatter.date }}" #2021-06-10T10:46:33+02:00
 draft: false
 summary: "{{ frontmatter.summary }}"
-author: "{{ frontmatter.author }}"
+authors: ["{{ frontmatter.author }}"]
 original_link: "{{ frontmatter.original_link }}"
 feed_name: "{{ frontmatter.feed_name}}"
 categories: ["{{ frontmatter.card_type }}", "{{ frontmatter.feed_name}}"]