Review/Update Contact Channels for RHAMT

We need to review and update the contact channels that are advertised within the documentation and the About Page of the static Reports. This should be done for 4.3.0.

We do have an internal Googlechat channel - should we advertise that for Red Hatters?

This originated from a query from Tobias (pasted below):

are we monitoring https://developer.jboss.org/en/windup ?

It's mentioned as channel in the docs https://access.redhat.com/documentation/en-us/red_hat_application_migration_toolkit/4.2/html/getting_started_guide/reference_material#important_links

There is also a reference to StackOverflow on our developers home: https://developers.redhat.com/products/rhamt/help

If you believe we should close any of these channels mentioned here, it would be good to update the docs accordingly.