docs: create volume spec page (#13353)

In addition to jobs, there are other objects in Nomad that have a
specific format and can be provided to commands and API endpoints.

This commit creates a new menu section to hold the specification for
volumes and update the command pages to point to the new centralized
definition.

Redirecting the previous entries is not possible with `redirect.js`
because they are done server-side and URL fragments are not accessible
to detect a match. So we provide hidden anchors with a link to the new
page to guide users towards the new documentation.

Co-authored-by: Tim Gross <tgross@hashicorp.com>

website/data/docs-nav-data.json

@@ -1418,6 +1418,36 @@
       }
     ]
   },
+  {
+    "title": "Other Specifications",
+    "routes": [
+      {
+        "title": "Overview",
+        "path": "other-specifications"
+      },
+      {
+        "title": "Volume",
+        "routes": [
+          {
+            "title": "Overview",
+            "path": "other-specifications/volume"
+          },
+          {
+            "title": "capability",
+            "path": "other-specifications/volume/capability"
+          },
+          {
+            "title": "mount_options",
+            "path": "other-specifications/volume/mount_options"
+          },
+          {
+            "title": "topology_request",
+            "path": "other-specifications/volume/topology_request"
+          }
+        ]
+      }
+    ]
+  },
   {
     "title": "Task Drivers",
     "routes": [