The root type of Matrix room events
to be sent by this network. Per the Matrix spec
(https://matrix.org/docs/spec/client_server/r0.6.1#room-event-fields),
this SHOULD be namespaced similar to Java package
naming conventions e.g. 'com.example.subdomain.event.type', so that different
programs use different eventTypes.
Also, if multiple MatrixWidgetNetworks appear in the
same webpage, they MUST use different rootEventTypes, or
else they will receive each other's messages.
Note that the user will be prompted to approve
the widget's use of this rootEventType, so it should
be comprehensible to end-users.
The actual event type used is
Generated using TypeDoc
[constructor description]