Add support for contact sensor (T110) (#877)

Initial support for T110 contact sensor & T110 fixture by courtesy of @ngaertner.

kasa/tests/smart/modules/test_contact.py

@@ -0,0 +1,29 @@
+import pytest
+
+from kasa import SmartDevice
+from kasa.smart.modules import ContactSensor
+from kasa.tests.device_fixtures import parametrize
+
+contact = parametrize(
+    "is contact sensor", model_filter="T110", protocol_filter={"SMART.CHILD"}
+)
+
+
+@contact
+@pytest.mark.parametrize(
+    "feature, type",
+    [
+        ("is_open", bool),
+    ],
+)
+async def test_contact_features(dev: SmartDevice, feature, type):
+    """Test that features are registered and work as expected."""
+    contact = dev.get_module(ContactSensor)
+    assert contact is not None
+
+    prop = getattr(contact, feature)
+    assert isinstance(prop, type)
+
+    feat = contact._module_features[feature]
+    assert feat.value == prop
+    assert isinstance(feat.value, type)