Implemented multiple webhooks (for e.g. connecting to multiple teams) in chat integrations.

The purpose is to allow chat-integrations from a base forum across multiple teams on MatterMost.

Example which motivated this extension: the Global Base creates post on the xrGlobal MatterMost team. My own community works primarily in the team xrScientists, and we would like to have similar posts there to highlight activity on the Base. I hope these reminders would encourage people to become more active there themselves.