Data: Documentation: Document undocumented declarations (#15176)

* Data: Documentation: Document plugins

* Data: Documentation: Document use

packages/data/README.md

@@ -358,7 +358,15 @@ _Returns_
 
 <a name="plugins" href="#plugins">#</a> **plugins**
 
-Undocumented declaration.
+Object of available plugins to use with a registry.
+
+_Related_
+
+-   [use](#use)
+
+_Type_
+
+-   `Object` 
 
 <a name="registerGenericStore" href="#registerGenericStore">#</a> **registerGenericStore**
 
@@ -470,7 +478,13 @@ _Parameters_
 
 <a name="use" href="#use">#</a> **use**
 
-Undocumented declaration.
+Extends a registry to inherit functionality provided by a given plugin. A
+plugin is an object with properties aligning to that of a registry, merged
+to extend the default registry behavior.
+
+_Parameters_
+
+-   _plugin_ `Object`: Plugin object.
 
 <a name="useRegistry" href="#useRegistry">#</a> **useRegistry**
 

packages/data/src/index.js

@@ -22,9 +22,17 @@ export {
 	AsyncModeProvider as __experimentalAsyncModeProvider,
 } from './components/async-mode-provider';
 export { createRegistry } from './registry';
-export { plugins };
 export { createRegistrySelector, createRegistryControl } from './factory';
 
+/**
+ * Object of available plugins to use with a registry.
+ *
+ * @see [use](#use)
+ *
+ * @type {Object}
+ */
+export { plugins };
+
 /**
  * The combineReducers helper function turns an object whose values are different
  * reducing functions into a single reducing function you can pass to registerReducer.
@@ -140,4 +148,12 @@ export const registerGenericStore = defaultRegistry.registerGenericStore;
  * @return {Object} Registered store object.
  */
 export const registerStore = defaultRegistry.registerStore;
+
+/**
+ * Extends a registry to inherit functionality provided by a given plugin. A
+ * plugin is an object with properties aligning to that of a registry, merged
+ * to extend the default registry behavior.
+ *
+ * @param {Object} plugin Plugin object.
+ */
 export const use = defaultRegistry.use;