Responsibility/Maintainer for each binding/package

We are getting a longer list of supported bindings/packages (which is great by the way 👍 )

Having said that, we need to make clear *who* is responsible for each package to keep up with updates et cetera (and also the consequences).

I tried to create an initial list. Please comment and/or provide feedback.

core thingweb team:
* core
* td-tools
* binding-coap
* binding-file
* binding-http
* cli
* examples
* browser-bundle

TBD:
* binding-opcua (core team? @erossignon ?)
* binding-mqtt (core team? @egekorkan @wiresio @sebastiankb ?)
* binding-netconf (@lukesmolo ?)
* binding-websockets (core team? @miguelrk ?)

@relu91
* binding-modbus

@hidetak
* binding-firestore-browser-bundle
* binding-firestore

@LennyHEVS @Chxresubles
* binding-mbus

Missing maintainer ? (--> on the list to be removed)
* binding-fujitsu @mryuichi ?
* binding-oracle @mlagally ?