Adds a top level menu item in the admin for Theme Documentation.
The plugin scans a folder contained in the theme called /documentation, plus subfolders, for .md files and builds a menu tree that loads the .md file when clicked.
Note: Any images contained in the .md files should use either an absolute URL or the relative path from the site's root.
EG:
https://www.example.com/wp-content/uploads/2023/08/image.jpg
-or-
/wp-content/themes/documentation/images/image/jpg
theme_docs_path_to_docs
URL path to documents folder.
theme_docs_uri_to_docs
URI path to documents folder.