Add coverage documentation to developer sidebar and fix rustfmt requirement

Co-authored-by: dannywillems <[email protected]>

Author: Copilot

website/sidebars.ts

@@ -68,6 +68,13 @@ const sidebars: SidebarsConfig = {
         'developers/updating-ocaml-node',
       ],
     },
+    {
+      type: 'category',
+      label: 'Development',
+      items: [
+        'developers/code-coverage',
+      ],
+    },
     {
       type: 'category',
       label: 'Architecture',