Dev Guide - Add new missing GeoServer Extensions

[ElenaGallo]

Description

Update the list of GeoServer Extensions here:

• Check for missing extensions and add them such as:
  • https://docs.geoserver.org/stable/en/user/community/wps-longitudinal-profile/index.html
• In WPS Extension add the WPS processes used by the GeoProcessing tool
• Check and fix existing hyperlinks and fix them if necessary
• The paragraph should be also moved on a better place in the dev documentation which is: intergations -> general -> geoserver

Documentation section involved

• User Guide
• Developer Guide

Other useful information

[tdipisa]

@ElenaGallo please fix the description as requested. Thank you.