Add markdown docs to "nav" configuration

[luccalb]

          Thank you for the mkdocs documentation web page updates.

Regarding with the changes there are 2 things which needs attention before we merge the pull request:
1 - There are markdown files which are listed in the docs directory but not included in the nav configuration. Let's add them in the nav at appropriate location.

2 - There is a reference to 'sdk/code-reference/pipelines/data_quality/data_manipulation/spark/delete_out_of_range_values.md' in the 'nav' configuration, which is not found in the documentation files. Which causes 404 page not found error at the web page:

Originally posted by @TugceOzberkYener in #126 (comment)