Update rtfd conf

[pradal]

Build the doc on readthedocs

[jbdurand]

I cannot build documentation using
make html
The command returns

sphinx-build -b html -d _build/doctrees   . _build/html
Running Sphinx v7.2.6

Configuration error:
There is a programmable error in your configuration file:

Traceback (most recent call last):
  File "/usr/lib/python3.12/importlib/metadata/__init__.py", line 397, in from_name
    return next(cls.discover(name=name))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
StopIteration

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/sphinx/config.py", line 358, in eval_config_file
    exec(code, namespace)  # NoQA: S102
    ^^^^^^^^^^^^^^^^^^^^^
  File "/home/jdurand/devlp/Git/openalea/StructureAnalysis/stat_tool/doc/conf.py", line 7, in <module>
    meta = metadata('openalea.' + pkg_name)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/importlib/metadata/__init__.py", line 879, in metadata
    return Distribution.from_name(distribution_name).metadata
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/importlib/metadata/__init__.py", line 399, in from_name
    raise PackageNotFoundError(name)
importlib.metadata.PackageNotFoundError: No package metadata was found for openalea.stat_tool

make: *** [Makefile:58 : html] Erreur 2