Support Form preferences

[relu91]

When deploying node-wot on a particular platform, developers might always prefer a particular protocol or content-type. We could introduce a configuration parameter at the servient level (or additionally as an extension to the scripting api consume function), to express this preference.

Example: (TDB)

const servient = new Servient();

[jona42-ui]

@relu91 would this fix the content negotiation bit of MQTT v5 user properties? say forexample when publishing messages, if the broker connection supports MQTT v5, injecting the contentType into the packet properties should allow consumers dynamically parse the payload. because it looks not supported.