Add deprecated to docs

lib/nimble_options/docs.ex

@@ -45,6 +45,7 @@ defmodule NimbleOptions.Docs do
 
     description =
       get_required_str(schema)
+      |> get_deprecated_str(schema)
       |> get_doc_str(schema)
       |> get_default_str(schema)
       |> case do
@@ -76,6 +77,13 @@ defmodule NimbleOptions.Docs do
     if schema[:required], do: "Required."
   end
 
+  defp get_deprecated_str(prev_str, schema) do
+    space_concat(
+      prev_str,
+      schema[:deprecated] && "This option is deprecated. #{String.trim(schema[:deprecated])}"
+    )
+  end
+
   defp get_doc_str(prev_str, schema) do
     space_concat(prev_str, schema[:doc] && String.trim(schema[:doc]))
   end

test/nimble_options/docs_test.exs

@@ -236,6 +236,22 @@ defmodule NimbleOptions.DocsTest do
       assert NimbleOptions.docs(schema) == docs
     end
 
+    test "generates deprecated information" do
+      schema = [
+        old: [type: :atom, doc: "Old option.", deprecated: "Use `:new` instead."],
+        new: [type: :string, doc: "New option."]
+      ]
+
+      docs = """
+      * `:old` (`t:atom/0`) - This option is deprecated. Use `:new` instead. Old option.
+
+      * `:new` (`t:String.t/0`) - New option.
+
+      """
+
+      assert NimbleOptions.docs(schema) == docs
+    end
+
     test "the option doesn't appear in the documentation when the :doc option is false" do
       schema = [
         name: [type: :atom, doc: "An atom."],