[mod] addition of various type hints / tbc

- pyright configuration [1]_
- stub files: types-lxml [2]_
- addition of various type hints
- enable use of new type system features on older Python versions [3]_
- ``.tool-versions`` - set python to lowest version we support (3.10.18) [4]_:
  Older versions typically lack some typing features found in newer Python
  versions.  Therefore, for local type checking (before commit), it is necessary
  to use the older Python interpreter.

.. [1] https://docs.basedpyright.com/v1.20.0/configuration/config-files/
.. [2] https://pypi.org/project/types-lxml/
.. [3] https://typing-extensions.readthedocs.io/en/latest/#
.. [4] https://mise.jdx.dev/configuration.html#tool-versions

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

searx/metrics/models.py

@@ -1,6 +1,8 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
 # pylint: disable=missing-module-docstring
 
+import typing as t
+
 import decimal
 import threading
 
@@ -135,16 +137,16 @@ class CounterStorage:  # pylint: disable=missing-class-docstring
 
     def clear(self):
         with self.lock:
-            self.counters = {}
+            self.counters: dict[t.Hashable, int] = {}
 
-    def configure(self, *args):
+    def configure(self, *args: str):
         with self.lock:
             self.counters[args] = 0
 
-    def get(self, *args):
+    def get(self, *args: str):
         return self.counters[args]
 
-    def add(self, value, *args):
+    def add(self, value: int, *args: str):
         with self.lock:
             self.counters[args] += value