add rendered_path in the template

guide/src/format/theme/index-hbs.md

@@ -23,6 +23,7 @@ Here is a list of the properties that are exposed:
 - ***book_title*** Title of the book, as specified in `book.toml`
 - ***chapter_title*** Title of the current chapter, as listed in `SUMMARY.md`
 
+- ***rendered_path*** Relative path to the rendered path from the source directory
 - ***path*** Relative path to the original markdown file from the source
   directory
 - ***content*** This is the rendered markdown.

src/renderer/html_handlebars/hbs_renderer.rs

@@ -95,6 +95,10 @@ impl HtmlHandlebars {
             ch.name.clone() + " - " + book_title
         };
 
+        let rendered_path = path.with_extension("html");
+
+        ctx.data
+            .insert("rendered_path".to_owned(), json!(rendered_path));
         ctx.data.insert("path".to_owned(), json!(path));
         ctx.data.insert("content".to_owned(), json!(content));
         ctx.data.insert("chapter_title".to_owned(), json!(ch.name));
@@ -124,6 +128,8 @@ impl HtmlHandlebars {
         utils::fs::write_file(&ctx.destination, &filepath, rendered.as_bytes())?;
 
         if ctx.is_index {
+            ctx.data
+                .insert("rendered_path".to_owned(), json!("index.html"));
             ctx.data.insert("path".to_owned(), json!("index.md"));
             ctx.data.insert("path_to_root".to_owned(), json!(""));
             ctx.data.insert("is_index".to_owned(), json!(true));
@@ -182,6 +188,7 @@ impl HtmlHandlebars {
             "/"
         };
         data_404.insert("base_url".to_owned(), json!(base_url));
+        data_404.insert("rendered_path".to_owned(), json!("404.html"));
         // Set a dummy path to ensure other paths (e.g. in the TOC) are generated correctly
         data_404.insert("path".to_owned(), json!("404.md"));
         data_404.insert("content".to_owned(), json!(html_content_404));
@@ -360,6 +367,7 @@ impl HtmlHandlebars {
         // the last rendered chapter by removing it from its context
         data.remove("title");
         data.insert("is_print".to_owned(), json!(true));
+        data.insert("rendered_path".to_owned(), json!("print.html"));
         data.insert("path".to_owned(), json!("print.md"));
         data.insert("content".to_owned(), json!(print_content));
         data.insert(