[Feature] Expose Tilt as CurrentHorizontalTiltAngle
**Problem description**
Hi, after adding my new device to zigbee-herdsman-converters (https://github.com/Koenkk/zigbee-herdsman-converters/pull/2474) I was quite surprised to not see the tilt value which it exposes in Homebridge. I guess no one until now had a scenario for this? 😄 

**Suggested solution**
We can use the tilt expose
```
{
     "access":7,
     "description":"Tilt of this cover",
     "name":"tilt",
     "property":"tilt",
     "type":"numeric",
     "value_max":100,
     "value_min":0
}
```
as a CurrentHorizontalTiltAngle characteristic with a little mapping of [0%, 100%] to [-90°,90°]. 
The same should then work for TargetHorizontalTiltAngle.

**Describe alternatives you've considered**
none, not implemented

**Additional context**
I have looked into the Cover converter, and position code can largely be imitated, but it should not be required like position,  rather optional as it is an optional characteristic.

**Are you willing to contribute to this feature?**
Yes, I am actively working on https://github.com/itavero/homebridge-z2m/pull/147
