docs: Add HCP link to navigation (#2722)

* docs: Add HCP link to navigation

* Add trailing slash

* Use relative path instead of absolute

* Change back to absolute link

* Change link to cloud.hashicorp

* Update name of product

website/data/docs-nav-data.json

@@ -520,6 +520,13 @@
   {
     "divider": true
   },
+  {
+    "title": "HCP Boundary",
+    "href": "https://cloud.hashicorp.com/docs/boundary/"
+  },
+  {
+    "divider": true
+  },
   {
     "title": "Release Notes",
     "routes": [