docs: Add missing groups_for_modules needed for docs import into ash_hq.

lib/reactor.ex

@@ -1,5 +1,7 @@
 defmodule Reactor do
-  @moduledoc ~S"""
+  alias Reactor.{Dsl, Executor, Info, Planner, Step}
+
+  @moduledoc """
   Reactor is a dynamic, concurrent, dependency resolving saga orchestrator.
 
   ## Usage
@@ -33,6 +35,19 @@ defmodule Reactor do
       ...> Reactor.run(reactor, %{whom: nil})
       {:ok, "Hello, World!"}
 
+  <!--- ash-hq-hide-start --> <!--- -->
+
+  ## DSL Documentation
+
+  ### Index
+
+  #{Spark.Dsl.Extension.doc_index(Dsl.sections())}
+
+  ### Docs
+
+  #{Spark.Dsl.Extension.doc(Dsl.sections())}
+
+  <!--- ash-hq-hide-stop --> <!--- -->
   """
 
   defstruct context: %{},
@@ -44,8 +59,6 @@ defmodule Reactor do
             state: :pending,
             steps: []
 
-  alias Reactor.{Dsl, Executor, Info, Planner, Step}
-
   use Spark.Dsl, default_extensions: [extensions: Dsl]
 
   @type context :: Enumerable.t({any, any})

lib/reactor/step.ex

@@ -1,6 +1,8 @@
 defmodule Reactor.Step do
   @moduledoc """
-  The struct used to store steps.
+  The Step behaviour and struct.
+
+  Implement this behaviour to make steps for your Reactor.
   """
 
   defstruct arguments: [], async?: true, impl: nil, name: nil, max_retries: :infinite, ref: nil

mix.exs

@@ -22,6 +22,11 @@ defmodule Reactor.MixProject do
         main: "readme",
         extras: extra_documentation(),
         groups_for_extras: extra_documentation_groups(),
+        groups_for_modules: [
+          DSL: ~r/^Reactor\.Dsl$/,
+          Steps: ~r/^Reactor\.Step.*/,
+          Internals: ~r/^Reactor\..*/
+        ],
         extra_section: "GUIDES",
         formatters: ["html"],
         filter_modules: ~r/^Elixir.Reactor/,