[docs][glossary] Add page that lists all standardized k8s terms (#5657)

* Add comprehensive glossary page

Additional Authors:
* Andrew Chen <chenopis@users.noreply.github.com>
* Steve Perry <steveperry-53@users.noreply.github.com>

* incorporate Tim's feedback

* address zach's comments

* address more comments

* add additional crosslinking

* Add platform developer, tweak formatting for disambiguation cases or multiparagraph definitions.

_data/glossary/cluster-operator.yaml

@@ -0,0 +1,16 @@
+id: cluster-operator
+name: Cluster Operator
+aka:
+  - Cluster Administrator
+related:
+  - cluster
+  - cluster-architect
+tags:
+  - user-type
+short-description: |
+  A person who configures, controls, and monitors clusters.
+
+long-description: |
+  Their primary responsibility is keeping a cluster up and running, which may involve periodic maintenance activities or upgrades.<br>
+
+  **NOTE:** Cluster operators are different from the [Operator pattern](https://coreos.com/operators) that extends the Kubernetes API.