Swedish weather institute weather component (#16717)

* SMHI Component

* Clean up typos

* Fixed default values first config to home location (tests will follow)

* Fixed tests and removed unused function

* Minor fixup after comments from @kane610

* add support for precipitation in forecast

* Removed old async_step_init not needed.

tests/components/smhi/common.py

@@ -0,0 +1,11 @@
+"""Common test utilities."""
+from unittest.mock import Mock
+
+
+class AsyncMock(Mock):
+    """Implements Mock async."""
+
+    # pylint: disable=W0235
+    async def __call__(self, *args, **kwargs):
+        """Hack for async support for Mock."""
+        return super(AsyncMock, self).__call__(*args, **kwargs)