[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/application-developer.yaml

@@ -0,0 +1,11 @@
+id: application-developer
+name: Application Developer
+related:
+  - application-architect
+tags:
+  - user-type
+short-description: |
+  A person who writes an application that runs in a Kubernetes cluster.
+long-description: >
+  An application developer focuses on one part of an application.
+  The scale of their focus may vary significantly in size.