docs: added examples page (#9587)

- Added an examples page with examples of all different concepts in Medusa. We'll probably add more examples with time as we see the need for them.
- Small fixes in different pages.

Preview: https://resources-docs-ocb5uyp0o-medusajs.vercel.app/v2/resources/examples

www/apps/book/app/basics/modules/page.mdx

@@ -127,7 +127,7 @@ The last step is to add the module in Medusa’s configurations.
 
 In `medusa-config.ts`, add a `modules` property and pass in it your custom module:
 
-```ts title="medusa-config.ts" highlights={[["6", "helloModuleService", "The key of the main service to be registered in the Medusa container."]]}
+```ts title="medusa-config.ts" highlights={[["7"]]}
 module.exports = defineConfig({
   projectConfig: {
     // ...