[Docs] Change mkdocs to not use directory urls (#18622)

Signed-off-by: mgoin <mgoin64@gmail.com>

mkdocs.yaml

@@ -119,3 +119,8 @@ extra_css:
 extra_javascript:
   - mkdocs/javascript/run_llm_widget.js
   - https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS_HTML
+
+# Makes the url format end in .html rather than act as a dir
+# So index.md generates as index.html and is available under URL /index.html
+# https://www.mkdocs.org/user-guide/configuration/#use_directory_urls
+use_directory_urls: false