docs: added directory structure documentation (#4612)

* docs: added directory structure documentation

* improvements

docs/content/development/entities/create.md

@@ -122,8 +122,8 @@ npm run build
 
 Then, run the `migration` command:
 
-```bash npm2yarn
-medusa migrations run
+```bash
+npx @medusajs/medusa-cli migrations run
 ```
 
 You should see that your migration have executed.

docs/content/development/entities/extend-entity.md

@@ -108,8 +108,8 @@ npm run build
 
 Then, run the following command to migrate your changes to the database:
 
-```bash npm2yarn
-medusa migrations run
+```bash
+npx @medusajs/medusa-cli migrations run
 ```
 
 You should see that your migration was executed, which means your changes were reflected in the database schema.

docs/content/development/entities/overview.mdx

@@ -68,6 +68,14 @@ If you want to remove a property from the `metadata` object, you can pass the `m
 
 ---
 
+## What are Repositories
+
+Repositories provide generic helper methods for entities. For example, a `list` method to retrieve all entities with pagination, or `retrieve` to retrieve a single entity record.
+
+Repostories are [Typeorm repositories](https://typeorm.io/working-with-repository), so you can refer to Typeorm's documentation on all available methods.
+
+---
+
 ## Custom Development
 
 Developers can create custom entities in the Medusa backend, a plugin, or in a module, then ensure it reflects in the database using a migration.