Don't strip relative path of additional javascript files

Previously, additional JavaScript files inside a directory were
correctly copied (with their parent created), but the link to it was
stripped of that parent.
There's no need for that (and it was not done for CSS)

src/renderer/html_handlebars/hbs_renderer.rs

@@ -422,13 +422,7 @@ fn make_data(
         for script in &html.additional_js {
             match script.strip_prefix(root) {
                 Ok(p) => js.push(p.to_str().expect("Could not convert to str")),
-                Err(_) => js.push(
-                    script
-                        .file_name()
-                        .expect("File has a file name")
-                        .to_str()
-                        .expect("Could not convert to str"),
-                ),
+                Err(_) => js.push(script.to_str().expect("Could not convert to str")),
             }
         }
         data.insert("additional_js".to_owned(), json!(js));