Add checkout order summary page (drupalcommerce#92)

* Add checkout order summary page

For drupalcommerce#34

* Add image and fix code block.

* Fix h2

.vscode/settings.json

@@ -1,6 +1,6 @@
 {
-    "restructuredtext.builtDocumentationPath" : "_build/html",
-    "restructuredtext.confPath"               : ".",
+    "restructuredtext.builtDocumentationPath" : "${workspaceRoot}/_build/html",
+    "restructuredtext.confPath"               : "${workspaceRoot}",
     "restructuredtext.updateOnTextChanged"    : "true",
     "restructuredtext.sphinxBuildPath": "sphinx-build",
     "python.linting.pylintEnabled": false

v2/checkout/index.rst

@@ -6,5 +6,6 @@ Configuring your checkout
 
    guest
    customize
+   order-summary
    checkout-pane-plugin
    creating-a-checkout-flow-plugin

v2/checkout/order-summary.rst

@@ -0,0 +1,26 @@
+Changing the order summary
+==========================
+
+Checkouts, by default, display an order summary on specific steps. This summary is powered by a view which can be modified. This is the *Checkout Order Summary* (`commerce_checkout_order_summary`) view. Changing this view will change how the order is displayed in summary during checkout.
+
+.. figure:: images/order-checkout-summary.png
+   :alt: Checkout Order Summary view
+
+Changing the view
+-----------------
+
+There is no user interface for changing the view provided. The view is added by the `CheckoutFlowBase` class when building the checkout flow form:
+
+.. code-block:: php
+
+    if ($this->hasSidebar($step_id)) {
+      $form['sidebar']['order_summary'] = [
+        '#type' => 'view',
+        '#name' => 'commerce_checkout_order_summary',
+        '#display_id' => 'default',
+        '#arguments' => [$this->order->id()],
+        '#embed' => TRUE,
+      ];
+    }
+
+To use a completely different view, you will need to use `hook_form_alter` to change the view name, or a provide a custom checkout flow plugin. 

v2/product/customize-the-shopping-cart-block.rst

@@ -42,6 +42,7 @@ The ``commerce_cart.layout.css`` and ``commerce_cart.theme.css`` files provide t
 
 
 .. highlight:: html
+
 libraries-override:
   commerce_cart/cart_block:
     css:
@@ -52,6 +53,7 @@ Or to completely disable the Cart stylesheet:
 
 
 .. highlight:: html
+
 libraries-override:
   commerce_cart/cart_block:
     css: