Hi everybody !
I’ve just received some Tuya WHD02 zigbee switches.
I thought after pairing in z2m that I will found some switches in the entities. But not.
So after reading tons of websites, I’ve finally found how to configure them. The exact syntax was hard to find !
I share for those who could be still searching 
In my configuration.yaml file, I’ve just added this (of course, replace Name_Given_In_Z2M by the real name you’ve typed) :
mqtt:
switch:
- state_topic: "zigbee2mqtt/Name_Given_In_Z2M"
command_topic: "zigbee2mqtt/Name_Given_In_Z2M/set"
unique_id: myswitch
name: "My Switch"
value_template: "{{ value_json.state }}"
payload_on: '{"state": "ON"}'
payload_off: '{"state": "OFF"}'
state_on: "ON"
state_off: "OFF"
Hope that can help.