Component: Panel has incomplete documentation of templates

[Kitsunay]

Describe the bug

Panel does not have documentation for template 'headericons', but it should. The template is referenced on field setters for 'expandIcon' and 'collapsedIcon' as '@deprecated since v15.4.2, use headericons template instead.', without further explanation on how to properly use the template. I had to read the source code of the panel component to find out what kind of HTML code should be passed as a template and that it also provides a context value of 'collapsed'.

This makes the process of changing two icons unnecessarily obtuse. Please, update the documentation to include the new way of changing the icons.

Environment

https://primeng.org/customicons
https://primeng.org/panel#template

Reproducer

No response

Angular version

17.3.12

PrimeNG version

17.18.11

Build / Runtime

Angular CLI App

Language

TypeScript

Node version (for AoT issues node --version)

20.18.0

Browser(s)

No response

Steps to reproduce the behavior

Compare documentation of panel component https://primeng.org/panel#template with panel code https://github.com/primefaces/primeng/blob/v18/src/app/components/panel/panel.ts

Expected behavior

I would expect the headericons template to be documented somewhere, preferably on the panel's documentation page.