[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

pyrightconfig.json

@@ -6,14 +6,21 @@
     "searxng_extra",
     "tests"
   ],
+
   "reportAny" : "information",
-  "enableTypeIgnoreComments": true,
-  "reportIgnoreCommentWithoutRule": true,
+  "reportConstantRedefinition": false,
+  "reportIgnoreCommentWithoutRule": "information",
+  "reportImplicitOverride": false,
   "reportImplicitStringConcatenation": false,
+  "reportImportCycles": "warning",
+  "reportMissingTypeStubs": "information",
   "reportUninitializedInstanceVariable": false,
   "reportUnnecessaryIsInstance": false,
+  "reportUnnecessaryTypeIgnoreComment": "error",
   "reportUnreachable": "information",
   "reportUnusedCallResult": false,
+
+  "enableTypeIgnoreComments": true,
   "executionEnvironments": [
     {
       "root": "searx",