Add documentation_url to the examples in docs.

Author: pivotal-marcela-campo

docs/v3/source/includes/api_resources/_service_offerings.erb

@@ -9,6 +9,7 @@
   "created_at": "2019-11-28T13:44:02Z",
   "updated_at": "2019-11-28T13:44:02Z",
   "shareable": true,
+  "documentation_url": "https://some-documentation-link.io",
   "broker_catalog": {
     "id": "db730a8c-11e5-11ea-838a-0f4fff3b1cfb",
     "metadata": {
@@ -76,6 +77,7 @@
       "created_at": "2019-11-28T13:44:02Z",
       "updated_at": "2019-11-28T13:44:02Z",
       "shareable": true,
+      "documentation_url": "https://some-documentation-link.io",
       "broker_catalog": {
         "id": "db730a8c-11e5-11ea-838a-0f4fff3b1cfb",
         "metadata": {
@@ -123,6 +125,7 @@
       "created_at": "2019-11-29T16:44:02Z",
       "updated_at": "2019-11-29T16:44:02Z",
       "shareable": true,
+      "documentation_url": "https://some-other-documentation-link.io",
       "broker_catalog": {
         "id": "3cb11822-12bb-11ea-beb1-a350dc7453b9",
         "metadata": {