Added option to output video date as part of the file output

[Howley1]

Added the option to output the video created date to the download chat e.g. running
chat_downloader https://zoom.us/rec/play/6ccrIuigqG83GIaT4wSDAv59W9W5J_-s1HUe_6UPykq3V3hVN1emMucTYLEJiA87rIkEPcGptB0Dp_dH --output {date_time}-{title}-chat.txt will output the file title as 2020-03-26 19_02_44-The History & Principles of Mutual Aid-chat.txt.
It will use the date that the video reports, so it might not be the actual broadcast date.

[glubsy]

I'm wondering if this is really necessary. Whoever calls the script can generate the output filename themselves and add their desired formatted date time to it. Unless I'm missing something specific to Zoom recordings?

See #234 for example, they have a wrapper script that generates the desired output filename that way.