Use the hchr field for Formaldehyde values

Reference discussion link: libdyson-wg/ha-dyson#4

The `hcho` field in MQTT is of an unknown unit/scale and has no known
conversion factor to a known unit. However, it was recently discovered
that `hchr` (referred to as "High Res Formaldehyde" in the android app)
has a clean conversion factor of n/1000 to mg/m^3.

libdyson/cloud/account.py

@@ -6,7 +6,7 @@
 import requests
 from requests.auth import AuthBase, HTTPBasicAuth
 
-from libdyson.exceptions import (
+from ..exceptions import (
     DysonAuthRequired,
     DysonInvalidAccountStatus,
     DysonInvalidAuth,

libdyson/dyson_device.py

@@ -259,7 +259,7 @@ def warning_code(self) -> str:
     @property
     def formaldehyde(self) -> Optional[int]:
         """Return formaldehyde reading."""
-        val = self._get_environmental_field_value("hcho")
+        val = self._get_environmental_field_value("hchr", divisor=1000)
         if val is None:
             return None
 

setup.cfg

@@ -1,6 +1,6 @@
 [metadata]
 name = libdyson-neon
-version = 1.0.2
+version = 1.1.0
 author = The libdyson Working Group
 author_email = [email protected]
 license = MIT License