Add support for Avatto Smart Wifi thermostat

Issue #279

Basic initial support for climate and child lock based on the iot.tuya.com
documentation.

There are many unknown attributes still, and many config features
(hysteresis, offsets, internal/external sensors, backlight brightness,
relay delay, probably fan speeds).

Using the debug method described in the zigbee2mqtt link in the README.md
can probably help to identify many of these (though experimentation will
be needed to map values onto their meanings in some cases).

custom_components/tuya_local/devices/avatto_wt100_thermostat.yaml

@@ -0,0 +1,134 @@
+name: Avatto WT100-EH thermostat
+primary_entity:
+  entity: climate
+  dps:
+    - id: 1
+      name: hvac_mode
+      type: boolean
+      mapping:
+        - dps_val: false
+          value: "off"
+        - dps_val: true
+          constraint: preset_mode
+          conditions:
+            - dps_val: cold
+              value: cool
+            - dps_val: hot
+              value: heat
+            - dps_val: wind
+              value: fan_only
+            - dps_val: comfortable
+              value: heat
+            - dps_val: energy
+              value: heat
+            - dps_val: auto
+              value: heat_cool
+            - dps_val: program
+              value: auto
+            - dps_val: holiday
+              value: auto
+            - dps_val: eco
+              value: heat
+            - dps_val: manual
+              value: heat
+            - dps_val: sleep
+              value: heat
+            - dps_val: dry
+              value: dry
+            - dps_val: floor_heat
+              value: heat
+            - dps_val: auxiliary_heat
+              value: heat
+    - id: 2
+      name: temperature
+      type: integer
+      range:
+        min: 0
+        max: 700
+      mapping:
+        - scale: 10
+    - id: 3
+      name: current_temperature
+      type: integer
+      mapping:
+        - scale: 10
+    - id: 4
+      name: preset_mode
+      type: string
+      mapping:
+        - dps_val: cold
+          value: Cool
+        - dps_val: hot
+          value: Heat
+        - dps_val: wind
+          value: Fan
+        - dps_val: comfortable
+          value: Comfort
+        - dps_val: energy
+          value: Energy
+        - dps_val: auto
+          value: Auto
+        - dps_val: holiday
+          value: Holiday
+        - dps_val: eco
+          value: Eco
+        - dps_val: manual
+          value: Manual
+        - dps_val: sleep
+          value: Sleep
+        - dps_val: dry
+          value: Dehumidify
+        - dps_val: program
+          value: Program
+        - dps_val: floor_heat
+          value: Floor Heating
+        - dps_val: auxiliary_heat
+          value: Auxiliary Heating
+    - id: 5
+      name: unknown_5
+      type: string
+    - id: 13
+      name: unknown_13
+      type: boolean
+    - id: 16
+      name: unknown_16
+      type: integer
+    - id: 20
+      name: unknown_20
+      type: integer
+    - id: 21
+      name: unknown_21
+      type: integer
+    - id: 25
+      name: unknown_25
+      type: string
+    - id: 26
+      name: unknown_26
+      type: boolean
+    - id: 31
+      name: unknown_31
+      type: boolean
+    - id: 41
+      name: unknown_41
+      type: string
+    - id: 42
+      name: unknown_42
+      type: string
+    - id: 101
+      name: unknown_101
+      type: boolean
+    - id: 105
+      name: unknown_105
+      type: integer
+    - id: 107
+      name: unknown_107
+      type: integer
+secondary_entities:
+  - entity: lock
+    name: Child lock
+    icon: "mdi:hand-back-right-off"
+    category: config
+    dps:
+      - id: 8
+        name: lock
+        type: boolean