Is your feature request related to a problem? Please describe.

My Slack has many more users than I care about, since I only care about a subset of conversations. Exporting all of them is a large waste of time and resources.

Describe the solution you'd like

I would like an option to build up the user information / cache as the desired channels and conversations are exported or dumped, rather than either not cache the information or not export the user information.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

1. Simply not having user information - Just userIDs has a certain "obfuscation" appeal, but still greatly reduces the usability of the export
2. Manually maintaining the user info file - Not appealing because there are still many users I do care about, and they get added over time, so manual maintenance would be burdensome
3. A way to update an existing user cache, rather than replace it - This would probably work, though given a large-enough set of users could still be burdensome

Additional context

None