Add Silvercrest HG06337-BS Wifi plug to Openhab

[anon71759204]

@Nocrys

By the way, I had it working in OH2.5 but I’ve not been able to make it work in OH3.

The German version of the plug (HG06337) works for me (openHABian / openHAB 3.2.0-SNAPSHOT - Build #2613, hacked Silvercrest gateway @ 6.7.8.0, openHAB ZigBee binding).