📘 Documentation update: reorganized endpoints

We have made some changes to the reference guide menus to improve navigation and clarity.

• People endpoints update: the "People" section now includes only the endpoints for the entire "employee" record or basic "fields" (not tables).
• Employee Tables: all other people APIs, which access employee tables, have been moved to the new "Employee Tables" section.
• Main page for each category: each category now has a main page that includes basic information about accessing these endpoints and their rate limits.

These enhancements aim to provide a more organized and user-friendly experience.