Fix section transparency serialization (#2462)

Fixes passing section.transparency for
https://github.com/getzola/zola/issues/1840

components/content/src/ser.rs

@@ -161,6 +161,7 @@ pub struct SerializingSection<'a> {
     translations: Vec<TranslatedContent<'a>>,
     backlinks: Vec<BackLink<'a>>,
     generate_feed: bool,
+    transparent: bool,
 }
 
 #[derive(Debug)]
@@ -220,6 +221,7 @@ impl<'a> SerializingSection<'a> {
             assets: &section.serialized_assets,
             lang: &section.lang,
             generate_feed: section.meta.generate_feed,
+            transparent: section.meta.transparent,
             pages,
             subsections,
             translations,

docs/content/documentation/templates/pages-sections.md

@@ -110,6 +110,8 @@ translations: Array<TranslatedContent>;
 backlinks: Array<{permalink: String, title: String?}>;
 // Whether this section generates a feed or not. Taken from the front-matter if set
 generate_feed: bool;
+// Whether this section is transparent. Taken from the front-matter if set
+transparent: bool;
 ```
 
 ## Table of contents