[CAL-1330] Whereby support subdomains

[PeerRich]

support subdomains in verification regex

_{From SyncLinear.com | CAL-1330}

[njyo]

For paid accounts Whereby provides the following meeting room options:
<subdomain>.whereby.com/<room_name>

This gets verified in 2 locations:

1. Set Whereby App as default [1]
2. Set Location to Whereby when editing an event type [2]

Thanks!

[1]

[2]

[njyo]

Thanks for the quick fix of this @PeerRich and @emrysal!