[glossary] Glossary MVP (#4865)

* [glossary] Glossary MVP

* resolve conflict

* initial pass at includable glossary data

* tag to term mapping

* Change StatefulSets to singular, StatefulSet

* revise glossary style guide, move

* make descriptions plural

_includes/templates/glossary/snippet.md

@@ -0,0 +1,25 @@
+{% assign term_data = site.data.glossary.[include.term] %}
+
+{% if term_data.short-description %}
+
+{{ term_data.short-description | markdownify }}
+
+{% else %}
+
+{% include templates/glossary/_error.md term=term_data.name missing_block='short-description' purpose='concisely describes the key term in 1-2 lines' %}
+
+{% endif %}
+
+{% if include.length == "long" %}
+
+{% if term_data.long-description %}
+
+{{ term_data.long-description | markdownify }}
+
+{% else %}
+
+{% include templates/glossary/_error.md term=term_data.name missing_block='long-description' purpose='describes the key term in greater depth, supplementing the short-description' %}
+
+{% endif %}
+
+{% endif %}