Document the selectors for the wc/store/checkout data store (#7085)

docs/third-party-developers/extensibility/data-store/README.md

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+# Data Store
+
+## Table of Contents
+
+-   [wc/store/checkout](checkout.md)
+
+<!-- FEEDBACK -->
+
+---
+
+[We're hiring!](https://woocommerce.com/careers/) Come work with us!
+
+🐞 Found a mistake, or have a suggestion? [Leave feedback about this document here.](https://github.com/woocommerce/woocommerce-blocks/issues/new?assignees=&labels=type%3A+documentation&template=--doc-feedback.md&title=Feedback%20on%20./docs/third-party-developers/extensibility/checkout-payment-methods/checkout-flow-and-events.md)
+
+<!-- /FEEDBACK -->

docs/third-party-developers/extensibility/data-store/checkout.md

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+# wc/store/checkout
+
+## Table of Contents
+
+-   [Selectors](#selectors)
+    -   [getCustomerId](#getcustomerid)
+    -   [getOrderNotes](#getordernotes)
+    -   [hasError](#haserror)
+    -   [hasOrder](#hasorder)
+    -   [isAfterProcessing](#isafterprocessing)
+    -   [isBeforeProcessing](#isbeforeprocessing)
+    -   [isCalculating](#iscalculating)
+    -   [isComplete](#iscomplete)
+    -   [isIdle](#isidle)
+    -   [isProcessing](#isprocessing)
+
+## Selectors
+
+### getCustomerId
+
+Returns the WordPress user ID of the customer whose order is currently processed by the Checkout block.
+
+#### _Returns_
+
+-   `number`: WordPress user ID of the customer.
+
+### getOrderNotes
+
+Returns the order notes.
+
+#### _Returns_
+
+-   `string`: Order notes.
+
+### hasError
+
+Returns true if an error occurred, and false otherwise.
+
+#### _Returns_
+
+-   `boolean`: Whether an error occurred.
+
+### hasOrder
+
+Returns true if a draft order had been created, and false otherwise.
+
+#### _Returns_
+
+-   `boolean`: Whether a draft order had been created.
+
+### isAfterProcessing
+
+Returns true if an order had just been processed, and false otherwise.
+
+#### _Returns_
+
+-   `boolean`: Whether an order had just been processed.
+
+### isBeforeProcessing
+
+Returns true if an order is about to be processed, and false otherwise.
+
+#### _Returns_
+
+-   `boolean`: Whether an order is about to be processed.
+
+### isCalculating
+
+Returns true if there is an in-flight request to update any values, and false otherwise.
+
+#### _Returns_
+
+-   `boolean`: Whether there is an in-flight request to update any values.
+
+### isComplete
+
+Returns true if the order is complete, and false otherwise.
+
+#### _Returns_
+
+-   `boolean`: Whether the order is complete.
+
+### isIdle
+
+Returns true if the checkout has had some activity, but is currently waiting for user input, and false otherwise.
+
+#### _Returns_
+
+-   `boolean`: Whether the checkout has had some activity, but is currently waiting for user input.
+
+### isProcessing
+
+Returns true if the checkout is processing, and false otherwise.
+
+#### _Returns_
+
+-   `boolean`: Whether the checkout is processing.
+
+<!-- FEEDBACK -->
+
+---
+
+[We're hiring!](https://woocommerce.com/careers/) Come work with us!
+
+🐞 Found a mistake, or have a suggestion? [Leave feedback about this document here.](https://github.com/woocommerce/woocommerce-blocks/issues/new?assignees=&labels=type%3A+documentation&template=--doc-feedback.md&title=Feedback%20on%20./docs/third-party-developers/extensibility/checkout-payment-methods/checkout-flow-and-events.md)
+
+<!-- /FEEDBACK -->