Add a literate tutorial for building emacs to the foreign documents test.

src/bin_foreign_document_test.rs

@@ -53,6 +53,9 @@ async fn main_body() -> Result<ExitCode, Box<dyn std::error::Error>> {
     let layer = layer.chain(compare_group("doomemacs", || {
         compare_all_org_document("/foreign_documents/doomemacs")
     }));
+    let layer = layer.chain(compare_group("literate_build_emacs", || {
+        compare_all_org_document("/foreign_documents/literate_build_emacs")
+    }));
 
     let running_tests: Vec<_> = layer.map(|c| tokio::spawn(c.run_test())).collect();
     let mut any_failed = false;