Update Checkout Module README Content

Author: ravi-chandra3197

app/code/Magento/Checkout/README.md

@@ -1,3 +1,33 @@
+# Magento_Checkout module
 Magento\Checkout module allows merchant to register sale transaction with the customer. Module implements consumer flow
 that includes such actions like adding products to cart, providing shipping and billing information and confirming
-the purchase.
+the purchase.
+
+#### Observer
+  This module observes the following events
+    `etc/events.xml`
+      `sales_quote_save_after` event in 
+      `Magento\Checkout\Observer\SalesQuoteSaveAfterObserver` file.
+    `/etc/frontend/events.xml`
+      `customer_login` event in `Magento\Checkout\Observer\LoadCustomerQuoteObserver`
+       file.
+      `customer_logout` event in `Magento\Checkout\Observer\UnsetAllObserver`
+  
+  ### Layouts
+  The module interacts with the following layout handles in the 
+    `view/frontend/layout`
+       `catalog_category_view`
+       `catalog_product_view`
+       `checkout_cart_configure`
+       `checkout_cart_configure_type_simple`
+       `checkout_cart_index`
+       `checkout_cart_item_renderers`
+       `checkout_cart_sidebar_item_price_renderers`
+       `checkout_cart_sidebar_item_renderers`
+       `checkout_cart_sidebar_total_renderers`
+       `checkout_index_index`
+       `checkout_item_price_renderers`
+       `checkout_onepage_failure`
+       `checkout_onepage_review_item_renderers`
+       `checkout_onepage_success`
+       `default`