Documentation for ajax does not mention FormData

It took me quite a while to find how to create an AJAX request with a fixed ordering of transferred arguments (even if the same name occurs multiple times) with a multipart/form-data encoding. I ended up posting a question to StackOverflow (https://stackoverflow.com/q/76545035/2240052) and found a related question with an answer that makes use of the following undocumented behavior of $.ajax:

• The data parameter can be a FormData object
• Setting contentType to false will in this case automatically create a correct contentType header including a boundary specification

This allowed me to solve my problem, but the documentation does not mention it and could be improved.

Start with the $.ajax documentation entry and review the data and contentType parameter sections. Document the FormData behavior and the contentType setting described in the issue; it is done when the multipart/form-data usage and boundary handling are clearly covered.