Add JustNimbus integration (#75718)

.coveragerc

CODEOWNERS

homeassistant/components/justnimbus/__init__.py

homeassistant/components/justnimbus/config_flow.py

homeassistant/components/justnimbus/const.py

homeassistant/components/justnimbus/coordinator.py

homeassistant/components/justnimbus/entity.py

homeassistant/components/justnimbus/manifest.json

homeassistant/components/justnimbus/sensor.py

homeassistant/components/justnimbus/strings.json

homeassistant/components/justnimbus/translations/en.json

homeassistant/generated/config_flows.py

requirements_all.txt

requirements_test_all.txt

tests/components/justnimbus/__init__.py

tests/components/justnimbus/test_config_flow.py