Sections in sitemaps don't get their [extra]

[Keats]

https://zola.discourse.group/t/sitemap-xml-no-extra-access-for-sections/240/2

Very easy to fix if someone wants to get a first try at Zola!

[stanistan]

👋 Hi, I'd like to take this on as a first issue... I'm assuming it starting here?

diff --git a/components/site/src/sitemap.rs b/components/site/src/sitemap.rs
index 72152f7..345cfb6 100644
--- a/components/site/src/sitemap.rs
+++ b/components/site/src/sitemap.rs
@@ -77,7 +77,11 @@ pub fn find_entries<'a>(
         .sections_values()
         .iter()
         .filter(|s| s.meta.render)
-        .map(|s| SitemapEntry::new(Cow::Borrowed(&s.permalink), None))
+        .map(|s| {
+            let mut entry = SitemapEntry::new(Cow::Borrowed(&s.permalink), None)
+            entry.add_extra(&s.meta.extra);
+            entry
+        })
         .collect::<Vec<_>>();
 
     for section in library.sections_values().iter().filter(|s| s.meta.paginate_by.is_some()) {

I can open up a PR for this...

Update: I see there's a bit more going on there :)