docs: improved SEO of documentation (#3117)

* docs: added description to documentation pages

* docs: added more descriptions

* docs: finished improving meta description

* docs: added searchbox structured data

* docs: added breadcrumbs structured data

* docs: added how to structured data

* docs: improved 404 page

* docs: added how-to frontmatter option

docs/content/advanced/backend/endpoints/add-middleware.md

@@ -1,3 +1,8 @@
+---
+description: 'Learn how to add a middleware in Medusa. A middleware is a function that has access to the request and response objects and can be used to perform actions around an endpoint.'
+addHowToData: true
+---
+
 # How to Add a Middleware
 
 In this document, you’ll learn how to add a middleware to an existing or custom route in Medusa.

docs/content/advanced/backend/endpoints/add.md

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+---
+description: 'Learn how to create endpoints in the Medusa server. This guide also includes how to add CORS configurations, creating multiple endpoints, adding protected routes, and more.'
+addHowToData: true
+---
+
 # How to Create Endpoints
 
 In this document, you’ll learn how to create endpoints in your Medusa server.