IBX-9609: Strict validation (#2666)

* mkdocs.yml: increase unrecognized_links strictness
* mkdocs.yml: increase omitted_files strictness
* mkdocs.yml: increase anchors strictness

Recommended in https://www.mkdocs.org/user-guide/configuration/#validation

Author: adriendupuis

mkdocs.yml

@@ -5,8 +5,14 @@ repo_url: https://github.com/ibexa/documentation-developer
 site_url: https://doc.ibexa.co/en/latest/
 copyright: "Copyright 1999-2024 Ibexa AS and others"
 validation:
-    links:
-        absolute_links: relative_to_docs
+    omitted_files: warn
+    absolute_links: relative_to_docs
+    unrecognized_links: warn
+    anchors: warn
+not_in_nav: |
+    search_results.md
+    personalization/legacy_recommendation_api.md
+    /snippets/*
 nav:
     - Ibexa Developer Documentation: index.md
     - Ibexa DXP editions: