Add docs for isCreateRestInstance function

Author: sergeysova

lib/index.js

@@ -27,7 +27,14 @@ import { createRestInstanceSymbol } from './symbol'
  * }
  */
 
-export const isCreateRestInstance = routing => routing[createRestInstanceSymbol] === true
+/**
+ * Check is correct routes passed
+ * @public
+ * @function
+ * @param {RestRoutes} routes
+ * @return {boolean}
+ */
+export const isCreateRestInstance = routes => routes[createRestInstanceSymbol] === true
 
 /**
  * @desc Routes object

lib/symbol.js

@@ -1 +1,4 @@
+/**
+ * @private
+ */
 export const createRestInstanceSymbol = Symbol('createRestInstance')