chore: adopt the NAPALM driver standard

- CI moves to .gitea/workflows/ci.yml and calls the shared driver workflow
  of NAPALM/driver-standard; .github/ is gone.
- requires-python >=3.10 (napalm-device-types needs it), floor
  napalm-device-types>=4.21.1 (was napalm_device_types>=0.4.0), LICENSE
  file, py.typed, SPDX license string, links to git.netork.io, a dev extra
  with floors.
- README (pyproject named one that did not exist) and CHANGELOG.md.
- mypy strict for the package; napalm_zyxel.zyxel_driver is exempt for now
  (24 errors), recorded in the quality baseline with its two complex
  functions. Coverage floor 68 % (measured 68.97 %).

Closes #8

tests/quality_baseline.json

@@ -0,0 +1,13 @@
+{
+ "coverage_floor": 68.0,
+ "function_complexity": {
+  "napalm_zyxel/zyxel_driver.py::ZyxelVMGDriver._parse_wireless_clients_dal": 12,
+  "napalm_zyxel/zyxel_driver.py::ZyxelVMGDriver.get_radio_status": 14
+ },
+ "function_lines": {},
+ "mypy_relaxed": [
+  "napalm_zyxel.zyxel_driver"
+ ],
+ "python_file_lines": {},
+ "untyped_public": []
+}