[Feature Request] Samsung Air Purifier 

**Describe the solution you'd like**
I would like the ability to control the Samsung AX5500K Air Purifier via homebridge

**Describe alternatives you've considered**
I have tried setting the Air Purifier as just a fan to be able to turn it on and off and select fan levels, but it gets reported on Apple Home as "Not Supported"

**Additional context**
This is the current log when trying to identify the Air Purifier in homebridge:

[12/8/2020, 2:13:43 pm] [SmartThings-v2] GOOD: Refreshing All Device Data
[12/8/2020, 2:13:45 pm] [SmartThings-v2] NOTICE: Temperature Unit is Now: (C)
[12/8/2020, 2:13:45 pm] [SmartThings-v2] WARN: Devices to Remove: (0) []
[12/8/2020, 2:13:45 pm] [SmartThings-v2] INFO: Devices to Update: (3)
[12/8/2020, 2:13:45 pm] [SmartThings-v2] GOOD: Devices to Create: (0) []
[12/8/2020, 2:13:45 pm] [SmartThings-v2] ERROR: initializeAccessory (fromCache: false) Error: this.getOrAddService is not a function TypeError: this.getOrAddService is not a function
    at DeviceCharacteristics.air_purifier (/usr/local/lib/node_modules/homebridge-smartthings/src/ST_DeviceCharacteristics.js:102:22)
    at /usr/local/lib/node_modules/homebridge-smartthings/src/ST_Accessories.js:107:48
    at Array.forEach (<anonymous>)
    at ST_Accessories.configureCharacteristics (/usr/local/lib/node_modules/homebridge-smartthings/src/ST_Accessories.js:103:22)
    at ST_Accessories.initializeAccessory (/usr/local/lib/node_modules/homebridge-smartthings/src/ST_Accessories.js:68:25)
    at ST_Platform.updateDevice (/usr/local/lib/node_modules/homebridge-smartthings/src/ST_Platform.js:193:55)
    at /usr/local/lib/node_modules/homebridge-smartthings/src/ST_Platform.js:153:61
    at Array.forEach (<anonymous>)
    at /usr/local/lib/node_modules/homebridge-smartthings/src/ST_Platform.js:153:38
    at runMicrotasks (<anonymous>)
[12/8/2020, 2:13:45 pm] [SmartThings-v2] ALERT: Total Initialization Time: (2 seconds)
[12/8/2020, 2:13:45 pm] [SmartThings-v2] NOTICE: Unknown Capabilities: ["Occupancy Sensor","Ocf","Execute","Air Quality Sensor","Odor Sensor","Dust Sensor","Very Fine Dust Sensor","Dust Health Concern","Fine Dust Health Concern","Very Fine Dust Health Concern","Air Conditioner Fan Mode","custom.airQualityMaxLevel","custom.welcomeCareMode","custom.airPurifierOperationMode","custom.filterUsageTime","custom.lowerDevicePower","custom.deviceDependencyStatus","custom.deviceReportStateConfiguration","custom.disabledCapabilities","custom.virusDoctorMode","samsungce.lamp","samsungce.driverVersion"]
[12/8/2020, 2:13:45 pm] [SmartThings-v2] INFO: SmartThings DeviceCache Size: (3)
[12/8/2020, 2:13:45 pm] [SmartThings-v2] INFO: Checking Package Version for Updates...
[12/8/2020, 2:13:47 pm] [SmartThings-v2] INFO: INFO: Your plugin version is up-to-date
[12/8/2020, 2:13:47 pm] [SmartThings-v2] NOTICE: Sending Plugin Status to SmartThings | UpdateAvailable: false | newVersion: 2.3.8
