docs: add cloud billing docs (#12766)

* docs: add cloud billing docs

* fixes

www/apps/cloud/generated/sidebar.mjs

@@ -113,6 +113,23 @@ export const generatedSidebars = [
           }
         ]
       },
+      {
+        "loaded": true,
+        "isPathHref": true,
+        "type": "category",
+        "title": "Billing",
+        "initialOpen": true,
+        "children": [
+          {
+            "loaded": true,
+            "isPathHref": true,
+            "type": "link",
+            "title": "Billing & Usage",
+            "path": "/billing-usage",
+            "children": []
+          }
+        ]
+      },
       {
         "loaded": true,
         "isPathHref": true,