inviteToGroup(userSteamID, groupSteamID) {
		let buffer = ByteBuffer.allocate(17, ByteBuffer.LITTLE_ENDIAN);
		buffer.writeUint64(Helpers.steamID(userSteamID).toString());
		buffer.writeUint64(Helpers.steamID(groupSteamID).toString());
		buffer.writeUint8(1); // unknown

		this._send(EMsg.ClientInviteUserToClan, buffer.flip());
	}
Invites a user to a Steam group. Only send group invites in response to a user's request; sending automated group
invites is a violation of the Steam Subscriber Agreement and can get you banned.
@param {(SteamID|string)} userSteamID - The SteamID of the user you're inviting as a SteamID object, or a string that can parse into one
@param {(SteamID|string)} groupSteamID - The SteamID of the group you're inviting the user to as a SteamID object, or a string that can parse into one