docs: document analytics module (#12563)

www/apps/book/app/learn/introduction/architecture/page.mdx

@@ -71,6 +71,7 @@ You can replace any of the third-party services mentioned above to build your pr
 
 [Infrastructure Modules](!resources!/infrastructure-modules) integrate third-party services and systems that customize Medusa's infrastructure. Medusa has the following Infrastructure Modules:
 
+- [Analytics Module](!resources!/infrastructure-modules/analytics): Tracks and analyzes user interactions and system events with third-party analytic providers. You can integrate [PostHog](!resources!/infrastructure-modules/analytics/posthog) as the analytics provider.
 - [Cache Module](!resources!/infrastructure-modules/cache): Caches data that require heavy computation. You can integrate a custom module to handle the caching with services like Memcached, or use the existing [Redis Cache Module](!resources!/infrastructure-modules/cache/redis).
 - [Event Module](!resources!/infrastructure-modules/event): A pub/sub system that allows you to subscribe to events and trigger them. You can integrate [Redis](!resources!/infrastructure-modules/event/redis) as the pub/sub system.
 - [File Module](!resources!/infrastructure-modules/file): Manages file uploads and storage, such as upload of product images. You can integrate [AWS S3](!resources!/infrastructure-modules/file/s3) for file storage.