docs: redesigned code blocks (#2745)

* docs: redesigned code blocks to include titles

* docs: added a title where necessary

docs/content/add-plugins/segment.md

@@ -102,7 +102,7 @@ Where `<YOUR_SEGMENT_WRITE_KEY>` is the Write Key shown on the page of the Segme
 
 Finally, in `medusa-config.js`, add the following new item to the `plugins` array:
 
-```jsx
+```jsx title=medusa-config.js
 const plugins = [
   //...
   {
@@ -142,7 +142,7 @@ In some cases, you might want to track more events or custom events. You can do
 
 For example, you can add the following subscriber to listen to the `customer.created` event and add tracking for every customer created:
 
-```jsx
+```jsx title=src/subscribers/customer.ts
 class CustomerSubscriber {
   constructor({ segmentService, eventBusService }) {
     this.segmentService = segmentService;