Move vocab doc into new reference dir

Author: mfisher87

for-instructors/style-guide.md

@@ -117,7 +117,7 @@ Follow the [Diátaxis](https://diataxis.fr) principles for your audience!
 
 ### Vocabulary
 
-All vocabulary should be defined in the [](../03-vocabulary.md) page.
+All vocabulary should be defined in the [](../reference/00-vocabulary.md) page.
 Follow the pre-existing pattern to add new terms.
 
 References should be conscious of case.

myst.yml

@@ -17,6 +17,9 @@ project:
     - title: "Materials"
       children:
         - pattern: "materials/0*/index.md"
+    - title: "Reference"
+      children:
+        - pattern: "reference/*.md"
     - title: "For instructors"
       children:
         - pattern: "for-instructors/*.md"