Added package usage examples to README

ghost/members-csv/README.md

@@ -10,7 +10,44 @@ or
 
 
 ## Usage
+There are 2 parts to this package: CSV to JSON serialization and JSON to CSV serialization. The module exposes 2 methods to fullfil these: `parse` and `unparse` respectively.
 
+To `parse` CSV file and convert it to JSON use `parse` method, e.g.:
+```js
+const {parse} = require('@tryghost/members-csv');
+
+const mapping = {
+    email: 'csv_column_containing_email_data',
+    name: 'csv_column_containing_names_data'
+}
+const membersJSON = await parse(csvFilePath, mapping);
+```
+
+`csvFilePath` - is a path to the CSV file that has to be processed
+`mapping` - optional parameter, it's a hash describing custom mapping for CSV columns to JSON properties
+
+Example mapping for CSV having email under `correo_electronico` column would look like following:
+```
+{
+    email: 'correo_electronico'
+}
+```
+
+To `unparse` JSON to CSV compatible with members format use following:
+```js
+const {unparse} = require('@tryghost/members-csv');
+
+const members = [{
+    email: 'email@example.com',
+    name: 'Sam Memberino',
+    note: 'Early supporter'
+}];
+
+const membersCSV = unparse(members);
+
+console.log(membersCSV);
+// -> "id,email,name,note,subscribed_to_emails,complimentary_plan,stripe_customer_id,created_at,deleted_at,labels\r\n,email@example.com,Sam Memberino,Early supporter,,,,,,"
+```
 
 ## Develop
 
@@ -36,4 +73,4 @@ Follow the instructions for the top-level repo.
 
 # Copyright & License 
 
-Copyright (c) 2020 Ghost Foundation - Released under the [MIT license](LICENSE).
+Copyright (c) 2020 Ghost Foundation - Released under the [MIT license](LICENSE).