Classic confinment for slack-mod-dark

slack-mod-dark is just repack of slack package that have classic confinment.
provide dark theme chat (only css is changed). this is required by many users, but can’t chage with snap package cause files is read only.

Please, accept.

@evan, @popey, @Wimpress, @Igor - can one of you perform the vetting for this snap? I’m not familiar with the slack snap, its developers, this snap or this snap’s developers (though the uploader isn’t from, but this feels like something that should be included in the official snap and not a fork of the proprietary slack snap.

I’m inclined to agree @jdstrand. This feels like something that should be offered as a contribution upstream. Perhaps @felix could comment on what the upstream feels about dark themes for slack, and whether those kinds of contributions from enthusiastic community members is welcome.

I’m going to mark this as “won’t fix” for now.

A dark mode in Slack is something that has been requested for a long time, and they just don’t listen, even though the workload on their side would be near zero, since these dark modes already exist. I’d honestly love to simply install a separate package with the dark mode applied as long as they refuse to do it themselves.