Feat: Add --channel-types cli argument

[ehrhart]

This adds an extra cli argument --channel-types which allows to specify which channel types to download messages from, thus bypassing the prompt dialog.

Example of usage:

yarn cli --automatic --channel-types public_channel,private_channel

[felixrieseberg]

Oh nice, thank you! Could you add a usage guide because I presume it doesn't handle spaces, right?

[ehrhart]

Something like this?

--channel-types             Comma-separated list of channel types to fetch messages from.
                            Example: --channel-types public_channel,private_channel,mpim,im

Also we might want to consider using a cli arguments parsing library such as yargs or commander in the future.

[felixrieseberg]

Thank you!