[mod] replace engines_languages.json by engines_traits.json

Implementations of the *traits* of the engines.

Engine's traits are fetched from the origin engine and stored in a JSON file in
the *data folder*.  Most often traits are languages and region codes and their
mapping from SearXNG's representation to the representation in the origin search
engine.

To load traits from the persistence::

    searx.enginelib.traits.EngineTraitsMap.from_data()

For new traits new properties can be added to the class::

    searx.enginelib.traits.EngineTraits

.. hint::

   Implementation is downward compatible to the deprecated *supported_languages
   method* from the vintage implementation.

   The vintage code is tagged as *deprecated* an can be removed when all engines
   has been ported to the *traits method*.

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

docs/conf.py

@@ -127,6 +127,10 @@ extensions = [
     'notfound.extension',  # https://github.com/readthedocs/sphinx-notfound-page
 ]
 
+autodoc_default_options = {
+    'member-order': 'groupwise',
+}
+
 myst_enable_extensions = [
   "replacements", "smartquotes"
 ]
@@ -135,6 +139,7 @@ suppress_warnings = ['myst.domains']
 
 intersphinx_mapping = {
     "python": ("https://docs.python.org/3/", None),
+    "babel" : ("https://babel.readthedocs.io/en/latest/", None),
     "flask": ("https://flask.palletsprojects.com/", None),
     "flask_babel": ("https://python-babel.github.io/flask-babel/", None),
     # "werkzeug": ("https://werkzeug.palletsprojects.com/", None),