VC/Zoom: add instructions for webhook configuration
VC/Zoom: add instructions for webhook configuration

ThiefMaster/indico-plugins,ThiefMaster/indico-plugins,ThiefMaster/indico-plugins,ThiefMaster/indico-plugins,indico/indico-plugins,indico/indico-plugins,indico/indico-plugins,indico/indico-plugins