css tweaks, cooking up an image banner

crates/treehouse/src/cli/generate.rs

@@ -24,7 +24,7 @@ use crate::{
         tree::branches_to_html,
     },
     state::Source,
-    tree::SemaRoots,
+    tree::{attributes::RootAttributes, SemaRoots},
 };
 
 use crate::state::{FileId, Treehouse};

crates/treehouse/src/html/tree.rs

@@ -56,9 +56,9 @@ pub fn branch_to_html(
                 BranchKind::Expanded => "<details open>",
                 BranchKind::Collapsed => "<details>",
             });
-            s.push_str("<summary>");
+            s.push_str("<summary class=\"branch-container\">");
         } else {
-            s.push_str("<div>");
+            s.push_str("<div class=\"branch-container\">");
         }
 
         s.push_str("<th-bp></th-bp>");

crates/treehouse/src/tree/attributes.rs

@@ -1,13 +1,21 @@
-use serde::Deserialize;
+use serde::{Deserialize, Serialize};
 
 /// Top-level `%%` root attributes.
-#[derive(Debug, Default, Clone, PartialEq, Eq, Deserialize)]
+#[derive(Debug, Default, Clone, PartialEq, Eq, Deserialize, Serialize)]
 pub struct RootAttributes {
     /// Title of the generated .html page.
     ///
     /// The page's tree path is used if empty.
     #[serde(default)]
     pub title: String,
+
+    /// Summary of the generated .html page.
+    #[serde(default)]
+    pub description: Option<String>,
+
+    /// ID of picture attached to the page, to be used as a thumbnail.
+    #[serde(default)]
+    pub thumbnail: Option<String>,
 }
 
 /// Branch attributes.