Add xtrude project to documentation (#4564)

Author: davidbrochart

doc/related-projects.rst

@@ -82,6 +82,7 @@ Visualization
 - `hvplot <https://hvplot.pyviz.org/>`_ : A high-level plotting API for the PyData ecosystem built on HoloViews.
 - `psyplot <https://psyplot.readthedocs.io>`_: Interactive data visualization with python.
 - `xarray-leaflet <https://github.com/davidbrochart/xarray_leaflet>`_: An xarray extension for tiled map plotting based on ipyleaflet.
+- `xtrude <https://github.com/davidbrochart/xtrude>`_: An xarray extension for 3D terrain visualization based on pydeck.
 
 Non-Python projects
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