structure the reference by categories

Author: ctoney

_pkgdown.yml

@@ -10,3 +10,15 @@ home:
   title: FIA stem map
   sidebar:
     structure: [toc, links, community, authors, citation, license]
+
+reference:
+- title: Datasets
+- contents:
+  - cw_coef
+  - cw_sapling_adj
+  - plantation
+
+- title: Functions
+- contents:
+  - crown_overlay_pct
+  - spatstat_helpers