[fix] engine & network issues / documentation and type annotations

This patch fixes some quirks and issues related to the engines and the network.
Each engine has its own network and this network was broken for the following
engines[1]:

- archlinux
- bing
- dailymotion
- duckduckgo
- google
- peertube
- startpage
- wikipedia

Since the files have been touched anyway, the type annotaions of the engine
modules has also been completed so that error messages from the type checker are
no longer reported.

Related and (partial) fixed issue:

- [1] https://github.com/searxng/searxng/issues/762#issuecomment-1605323861
- [2] https://github.com/searxng/searxng/issues/2513
- [3] https://github.com/searxng/searxng/issues/2515

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

searx/enginelib/__init__.py

@@ -17,7 +17,7 @@
 
 
 from __future__ import annotations
-from typing import Union, Dict, List, Callable, TYPE_CHECKING
+from typing import List, Callable, TYPE_CHECKING
 
 if TYPE_CHECKING:
     from searx.enginelib import traits
@@ -134,3 +134,15 @@ class Engine:  # pylint: disable=too-few-public-methods
           require_api_key: true
           results: HTML
     """
+
+    using_tor_proxy: bool
+    """Using tor proxy (``true``) or not (``false``) for this engine."""
+
+    send_accept_language_header: bool
+    """When this option is activated, the language (locale) that is selected by
+    the user is used to build and send a ``Accept-Language`` header in the
+    request to the origin search engine."""
+
+    tokens: List[str]
+    """A list of secret tokens to make this engine *private*, more details see
+    :ref:`private engines`."""