#857 Add a API quickstart page under the (to be added) API section (#858)

* initial engineering draft of api quickstart

* spacing, headings

* copyedit

* note syntax added for last warning

* link to create api keys page, copy edits

* formating

* Apply suggestions from code review

Co-authored-by: Billy Tat <btat@suse.com>

* indentation, intro

* Update docs/api/quickstart.md

Co-authored-by: Billy Tat <btat@suse.com>

* Apply suggestions from code review

Co-authored-by: Michael Bolot <michael.bolot@suse.com>

* Update docs/api/quickstart.md

* removed commented-out line

* moved text from step 5 to step 3, made  into its own step, added info about not all resources offering detailed output

* added sidebar entry

* mv'd to version-2.8 dir

* rm'd remainders in /docs dir

---------

Co-authored-by: Billy Tat <btat@suse.com>
Co-authored-by: Michael Bolot <michael.bolot@suse.com>

versioned_sidebars/version-2.8-sidebars.json

@@ -1305,6 +1305,16 @@
         }
       ]
     },
+    {
+      "type": "category",
+      "label": "Rancher Kubernetes API",
+      "items": [
+        "api/quickstart",
+        {
+
+        }
+      ]
+    },
     "contribute-to-rancher",
     {
       "type": "category",