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/price-selection-strategy/index.md

@@ -1,3 +1,7 @@
+---
+description: 'Learn what the price selection strategy is in the Medusa server. The price selection strategy retrieves the best price for a product variant for a specific context.'
+---
+
 # Price Selection Strategy
 
 In this document, you’ll learn what a price selection strategy is.

docs/content/advanced/backend/price-selection-strategy/override.md

@@ -1,4 +1,9 @@
-# Override Price Selection Strategy
+---
+description: 'Learn how to override the price selection strategy. The price selection strategy is used to determine the best price based on a specific context.'
+addHowToData: true
+---
+
+# How to Override Price Selection Strategy
 
 In this document, you’ll learn how to override Medusa’s price selection strategy to create a custom pricing strategy.