Update "Development documentation"

Update master with new doc structure and triggering hysop-doc CI on master changes.

ci/docker_images/ubuntu/jammy/Dockerfile

@@ -240,7 +240,7 @@ RUN cd /tmp && \
 
 # Tools for building documentation
 RUN apt-get update && apt-get install -y graphviz && apt-get install -y doxygen
-RUN ${PYTHON_EXECUTABLE} -m pip install sphinx sphinxcontrib-bibtex sphinxcontrib-doxylink sphinx_bootstrap_theme strip-hints
+RUN ${PYTHON_EXECUTABLE} -m pip install sphinx sphinxcontrib-bibtex sphinxcontrib-doxylink sphinx_bootstrap_theme sphinx-rtd-theme strip-hints
 
 RUN ${PYTHON_EXECUTABLE} -m pip install ansicolors --ignore-installed
 RUN ${PYTHON_EXECUTABLE} -m pip install numpy==1.21.5