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/add-plugins/contentful/customize-contentful.md

@@ -1,3 +1,8 @@
+---
+description: 'Learn how to customize the Contentful integration with Medusa and how to customize the Gatsby storefront that is connected to Contentful.'
+addHowToData: true
+---
+
 # Customize your Medusa and Contentful Integration
 
 In this document, you’ll learn how to customize the Contentful integration with Medusa and how to customize the Gatsby storefront that is connected to Contentful.

docs/content/add-plugins/contentful/index.md

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+---
+description: 'Learn how to integrate Contentful with the Medusa server and a Gatsby storefront. Contentful is a headless CMS server that provides rich CMS functionalities.'
+addHowToData: true
+---
+
 # Contentful
 
 In this document, you’ll learn how to integrate a Medusa server with Contentful to add rich Content Management System (CMS) functionalities