Changes for Homebridge 2.0

#301 Initial fixes to make the plugin work with Homebridge 2.0
Two basic changes:
1. Use of enums off the Characteristic class is no longer supported:
Instead of const Units = Characteristic.Units; you will need to use const Units = api.hap.Units;
Instead of const Formats = Characteristic.Formats; you will need to use const Formats = api.hap.Formats;
Instead of const Perms = Characteristic.Perms; you will need to use const Perms = api.hap.Perms;

2. Change custom characteristics to be classes with constructors, rather than using the inherits() functionality.

index.js

@@ -45,7 +45,7 @@ function WeatherPlusPlatform(_log, _config)
 
 	// Custom Services and Characteristics
 	CustomService = require("./util/services")(Service, Characteristic);
-	CustomCharacteristic = require("./util/characteristics")(Characteristic, this.units);
+	CustomCharacteristic = require("./util/characteristics")(Characteristic, HomebridgeAPI, this.units);
 	CurrentConditionsWeatherAccessory = require("./accessories/currentConditions")(Service, Characteristic, CustomService, CustomCharacteristic, FakeGatoHistoryService);
 	ForecastWeatherAccessory = require("./accessories/forecast")(Service, Characteristic, CustomService, CustomCharacteristic);
 

package.json

@@ -44,8 +44,8 @@
     "weatherflow weather station"
   ],
   "engines": {
-    "node": ">=10.0.0",
-    "homebridge": ">=1.0.0"
+    "node": ">=10.0.0 || ^20.15.1",
+    "homebridge": ">=1.0.0 || ^2.0.0-beta.0"
   },
   "author": {
     "name": "Arne Blumentritt",