doc: releases: add more release highlights for 4.0

Major enhancements with this release include:

* The introduction of the :ref:`secure storage<secure_storage>` subsystem. It allows the use of the

  PSA Secure Storage API and of persistent keys in the PSA Crypto API on all board targets. It

* **Secure Storage Subsystem**:

  A newly introduced :ref:`secure storage<secure_storage>` subsystem allows the use of the

  PSA Secure Storage API and of persistent keys in the PSA Crypto API on *all* board targets. It

  is now the standard way to provide device-specific protection to data at rest. (:github:`76222`)

* The introduction of the :ref:`comparator<comparator_api>` device driver subsystem for analog

  comparators, complete with shell support. It supports initial configuration through devicetree

  and runtime configuration through vendor specific APIs. Initially the

  :dtcompatible:`nordic,nrf-comp`, :dtcompatible:`nordic,nrf-lpcomp` and

  :dtcompatible:`nxp,kinetis-acmp` are supported.

* **ZMS (Zephyr Memory Storage) Subsystem**:

  :ref:`ZMS <zms_api>` is a new key-value storage subsystem compatible with all non-volatile storage

  types, including traditional NOR flash and advanced technologies like RRAM and MRAM that support

  write without erasure.

* The introduction of the :ref:`stepper<stepper_api>` device driver subsystem for stepper motors,

  complete with shell support. Initially implemented drivers include a simple

  :dtcompatible:`zephyr,gpio-stepper` and a complex sensor-less stall-detection capable with

  integrated ramp-controller :dtcompatible:`adi,tmc5041`.

* **Analog Comparators**:

  A new :ref:`comparator<comparator_api>` device driver subsystem for analog comparators has been

  added, complete with shell support. It supports initial configuration through Devicetree and

  runtime configuration through vendor specific APIs. Initially the :dtcompatible:`nordic,nrf-comp`,

  :dtcompatible:`nordic,nrf-lpcomp` and :dtcompatible:`nxp,kinetis-acmp` are supported.

* **Stepper Motors**:

  It is now possible to interact with stepper motors using a standard API thanks to the new

  :ref:`stepper<stepper_api>` device driver subsystem, which also comes with shell support.

  Initially implemented drivers include a simple :dtcompatible:`zephyr,gpio-steppers` and a complex

  sensor-less stall-detection capable with integrated ramp-controller :dtcompatible:`adi,tmc5041`.

* **Haptics**:

  A new :ref:`haptics_api` device driver subsystem allows unified access to haptic controllers,

  enabling users to add haptic feedback to their applications.

* **Multimedia Capabilities**

  Zephyr's audio and video capabilities have been expanded with support for new image sensors, video

  interfaces, audio interfaces, and codecs being supported.

* **Prometheus Library**:

  A `Prometheus`_ metrics library has been added to the networking stack. It provides a way to

  expose metrics to Prometheus clients over HTTP, facilitating the consolidated remote monitoring of

  Zephyr devices alongside other systems typically monitored using Prometheus.

* **Documentation Improvements**:

  Several enhancements were made to the online documentation to improve content discovery and

  navigation. These include a new :ref:`interactive board catalog <boards>` and an interactive

  directory for :zephyr:code-sample-category:`code samples <samples>`.

* **Expanded Board Support**:

  Over 60 :ref:`new boards <boards_added_in_zephyr_4_0>` and

  :ref:`shields <shields_added_in_zephyr_4_0>` are supported in Zephyr 4.0.

.. _`Prometheus`: https://prometheus.io/

An overview of the changes required or recommended when migrating your application from Zephyr

v3.7.0 to Zephyr v4.0.0 can be found in the separate :ref:`migration guide<migration_4.0>`.

  * NXP mimxrt685: fixed clocks to enable DMIC

  * NXP MCX N Series: Fixed NXP LPSPI native chip select when using synchronous API with DMA bug

.. _boards_added_in_zephyr_4_0:

* Added support for these boards:

   * :zephyr:board:`01space ESP32C3 0.42 OLED <esp32c3_042_oled>` (``esp32c3_042_oled``)

  * Enabled ENET ethernet on NXP ``imx8mm`` and ``imx8mn``

  * Added support for the NXP ``imx8qm`` and ``imx8qxp`` DSP core to enable the openAMP sample

.. _shields_added_in_zephyr_4_0:

* Added support for the following shields:

  * :ref:`ADI EVAL-ADXL362-ARDZ <eval_adxl362_ardz>`