💡 idea: add a data-preloaded Mattermost server to facilitate demos and testing

[azigler]

Description

The barrier for setting up the Mattermost AI Copilot on a new server and testing it with data is too high, given a fresh server has no messages that can be utilized with the AI therefore demo messages/content must first be created and added in order to try out the tool. The only alternative is testing on a server with actual testing, which is not feasible in many cases.

A proposed solution is to create a branch or directory in this repository that includes a Mattermost server and accompanying Postgres database that is preloaded with data for experimenting with and testing the plugin.