Add the chat toggle action

[matthijs110]

While I was researching and reverse engineering the Microsoft Teams plugin of the Elgato Stream Deck, I noticed an action called ToggleChat:

// meetingController.js
TeamsMeetingController.prototype.toggleChat = function () {
    this.sendMeetingActionRequestToTeams("toggle-ui" /* ToggleUI */, "chat");
};

The toggle-ui action with the chat parameter toggles the chat window on the right side of a call window.