docs: add type hints to examples (things.py, things_asgi.py, things_advanced_asgi.py)

[Midhun1618]

Summary of Changes

Added type annotations to three example files as part of #1820:

• examples/things.py — added from falcon import Request, Response and typed the on_get responder
• examples/things_asgi.py — added from falcon.asgi import Request, Response and typed the on_get responder
• examples/things_advanced_asgi.py — added from falcon.asgi import Request, Response and from typing import Any, typed all responder methods, middleware process methods, hook functions, and helper methods throughout

Related Issues

#1820

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• Applied changes to both WSGI and ASGI code paths and interfaces (where applicable).
• Added tests for changed code.
• Performed automated tests and code quality checks by running tox.
• Prefixed code comments with GitHub nick and an appropriate prefix.
• Coding style is consistent with the rest of the framework.
• Updated documentation for changed code.
  • Added docstrings for any new classes, functions, or modules.
  • Updated docstrings for any modifications to existing code.
  • Updated both WSGI and ASGI docs (where applicable).
  • Added references to new classes, functions, or modules to the relevant RST file under docs/.
  • Updated all relevant supporting documentation files under docs/.
  • A copyright notice is included at the top of any new modules (using your own name or the name of your organization).
  • Changed/added classes/methods/functions have appropriate versionadded, versionchanged, or deprecated directives.
• Changes (and possible deprecations) have towncrier news fragments under docs/_newsfragments/.
• LLM output, if any, has been carefully reviewed and tested by a human developer.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (b1b683a) to head (1cb9787).

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2639   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           64        64           
  Lines         7976      7976           
  Branches      1102      1102           
=========================================
  Hits          7976      7976           

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