Allow setting card per page/section

CHANGELOG.md

@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add `h1` with page/section title by default.
 - Add ability to set accent color per page/section.
 - Add ability to set default theme per page/section.
+- Add ability to set metadata card per page/section.
 - Add active state to footer's "Powered by" links.
 - Add active state to footnotes' go back button.
 - Add active state to slider thumb.

templates/partials/card.html

@@ -1,6 +1,10 @@
-{%- if page.extra.banner -%}
-    {%- set card = resize_image(path=page.colocated_path ~ page.extra.banner, width=1200, height=628, op="fill") -%}
-    {{ card.url }}
+{%- if page.extra.card -%}
+	{{ get_url(path=page.colocated_path ~ page.extra.card) }}
+{%- elif section.extra.card -%}
+	{{ get_url(path=section.colocated_path ~ section.extra.card) }}
+{%- elif page.extra.banner -%}
+	{%- set card = resize_image(path=page.colocated_path ~ page.extra.banner, width=1200, height=628, op="fill") -%}
+	{{ card.url }}
 {%- else -%}
-    {{ get_url(path='card.png') }}
+	{{ get_url(path='card.png') }}
 {%- endif -%}