Minor adjustments to Strat module docs

docs/make.jl

@@ -36,7 +36,7 @@ makedocs(modules=modules,
                             "Heat Conduction" => "api/heat_conduction.md",
                             "Surface Energy Balance" => "api/seb.md",
                        ],
-                       "Strat" => "api/strat.md",
+                       "Stratigraphy" => "api/strat.md",
                        "Diagnostics" => "api/diagnostics.md",
                        "Presets" => "api/presets.md",
                 ],

docs/src/api/strat.md

 # Strat
 
+This module contains the `Stratigraphy`, `Tile`, and related types for building and evaluating a CryoGrid 1-D process model.
+
 ```@autodocs
 Modules = [Strat]
 Private = false