Use .readthedocs.yaml for building ReadTheDocs's content.

[evshary]

RTD requests the migration of configuration v2:
https://blog.readthedocs.com/migrate-configuration-v2/

I use the default configuration here and see whether it works or not.

[evshary]

@Mallets could you please check whether the issue still exists after merging the PR?
I'm not sure where to see the migration warning (Maybe only in mail?)

[cguimaraes]

This PR broke readthedocs documentation generation:

Running Sphinx v1.8.6

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/zenoh-pico/envs/latest/lib/python3.11/site-packages/sphinx/config.py", line 368, in eval_config_file
    execfile_(filename, namespace)
  File "/home/docs/checkouts/readthedocs.org/user_builds/zenoh-pico/envs/latest/lib/python3.11/site-packages/sphinx/util/pycompat.py", line 150, in execfile_
    exec_(code, _globals)
  File "/home/docs/checkouts/readthedocs.org/user_builds/zenoh-pico/checkouts/latest/docs/conf.py", line 18, in <module>
    from clang.cindex import Config
ModuleNotFoundError: No module named 'clang'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/zenoh-pico/envs/latest/lib/python3.11/site-packages/sphinx/cmd/build.py", line 300, in build_main
    app = Sphinx(args.sourcedir, args.confdir, args.outputdir,
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/docs/checkouts/readthedocs.org/user_builds/zenoh-pico/envs/latest/lib/python3.11/site-packages/sphinx/application.py", line 201, in __init__
    self.config = Config.read(self.confdir, confoverrides or {}, self.tags)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/docs/checkouts/readthedocs.org/user_builds/zenoh-pico/envs/latest/lib/python3.11/site-packages/sphinx/config.py", line 203, in read
    namespace = eval_config_file(filename, tags)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/docs/checkouts/readthedocs.org/user_builds/zenoh-pico/envs/latest/lib/python3.11/site-packages/sphinx/config.py", line 380, in eval_config_file
    raise ConfigError(msg % traceback.format_exc())
sphinx.errors.ConfigError: There is a programmable error in your configuration file:

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/zenoh-pico/envs/latest/lib/python3.11/site-packages/sphinx/config.py", line 368, in eval_config_file
    execfile_(filename, namespace)
  File "/home/docs/checkouts/readthedocs.org/user_builds/zenoh-pico/envs/latest/lib/python3.11/site-packages/sphinx/util/pycompat.py", line 150, in execfile_
    exec_(code, _globals)
  File "/home/docs/checkouts/readthedocs.org/user_builds/zenoh-pico/checkouts/latest/docs/conf.py", line 18, in <module>
    from clang.cindex import Config
ModuleNotFoundError: No module named 'clang'


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

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/zenoh-pico/envs/latest/lib/python3.11/site-packages/sphinx/config.py", line 368, in eval_config_file
    execfile_(filename, namespace)
  File "/home/docs/checkouts/readthedocs.org/user_builds/zenoh-pico/envs/latest/lib/python3.11/site-packages/sphinx/util/pycompat.py", line 150, in execfile_
    exec_(code, _globals)
  File "/home/docs/checkouts/readthedocs.org/user_builds/zenoh-pico/checkouts/latest/docs/conf.py", line 18, in <module>
    from clang.cindex import Config
ModuleNotFoundError: No module named 'clang'

Note that although the badge is showing as failed, it was still build successfully until the change was made mandatory.

Your project(s) "zenoh-pico" don't have a configuration file. Configuration files will soon be required by projects, and will no longer be optional. [Read our blog post to create one](https://blog.readthedocs.com/migrate-configuration-v2/) and ensure your project continues building successfully.