Adding sub-parts

app/templates/_nav.html

@@ -23,6 +23,9 @@
     {% if user.is_superuser or "part_types:read" in user.permissions %}
       <a href="/admin/part-types">Part Types</a>
     {% endif %}
+    {% if user.is_superuser or "sub_part_types:read" in user.permissions %}
+      <a href="/admin/sub-part-types">Sub Part Types</a>
+    {% endif %}
     {% if user.is_superuser or "audit_log:read" in user.permissions %}
       <a href="/admin/audit-log">Audit Log</a>
     {% endif %}