Add missing CSS file for settings page

Author: GuillaumeGomez

src/librustdoc/html/render/context.rs

@@ -596,9 +596,11 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             |buf: &mut Buffer| {
                 write!(
                     buf,
-                    "<script defer src=\"{}settings{}.js\"></script>",
-                    page.static_root_path.unwrap_or(""),
-                    page.resource_suffix
+                    "<link rel=\"stylesheet\" type=\"text/css\" \
+                        href=\"{root_path}settings{suffix}.css\">\
+                    <script defer src=\"{root_path}settings{suffix}.js\"></script>",
+                    root_path = page.static_root_path.unwrap_or(""),
+                    suffix = page.resource_suffix,
                 )
             },
             &self.shared.style_files,