doc: develop: manifests: external: add zenoh-pico

Introduce documentation for using zenoh-pico as an external module in
Zephyr.

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>

Author: kartben

doc/develop/manifest/external/zenoh-pico.rst

@@ -0,0 +1,58 @@
+.. _external_module_zenoh_pico:
+
+zenoh-pico
+##########
+
+Introduction
+************
+
+`zenoh-pico`_ is the `Eclipse Zenoh`_ implementation that targets constrained devices, offering a
+native C API. It provides Zero Overhead Pub/sub, Store/Query and Compute capabilities for embedded
+systems and microcontrollers.
+
+zenoh-pico unifies data in motion, data at rest, and computations while retaining time and space
+efficiency well beyond mainstream stacks. It is fully compatible with the main Rust Zenoh
+implementation, providing a lightweight implementation of most functionalities.
+
+zenoh-pico is licensed under the Eclipse Public License 2.0 and Apache License 2.0.
+
+Usage with Zephyr
+*****************
+
+The zenoh-pico repository is a Zephyr :ref:`module <modules>` which provides distributed
+communication capabilities to Zephyr applications. It supports UDP (unicast and multicast), TCP
+transport layers over IPv4, IPv6, and 6LoWPAN networks with WiFi, Ethernet, Thread, and Serial data
+link layers.
+
+To pull in zenoh-pico as a Zephyr module, either add it as a West project in the ``west.yaml``
+file or pull it in by adding a submanifest (e.g. ``zephyr/submanifests/zenoh-pico.yaml``) file
+with the following content and run ``west update``:
+
+.. code-block:: yaml
+
+   manifest:
+     projects:
+       - name: zenoh-pico
+         url: https://github.com/eclipse-zenoh/zenoh-pico.git
+         revision: main
+         path: modules/lib/zenoh-pico # adjust the path as needed
+
+For more detailed instructions and API documentation, refer to the `zenoh-pico documentation`_ as
+well as the provided `Zephyr examples`_.
+
+References
+**********
+
+.. target-notes::
+
+.. _zenoh-pico:
+   https://github.com/eclipse-zenoh/zenoh-pico
+
+.. _Eclipse Zenoh:
+   https://zenoh.io
+
+.. _zenoh-pico documentation:
+   https://zenoh-pico.readthedocs.io/en/latest/
+
+.. _Zephyr examples:
+   https://github.com/eclipse-zenoh/zenoh-pico/tree/main/examples/zephyr