[docs-infra] Split Slack channel per team

[oliviertassinari]

Summary

We have these feedback channels today:

• docs-feedback
• docs-feedback-x
• docs-feedback-toolpad

Soon or later, we will want:

• docs-feedback-base-ui
• docs-feedback-material-ui
• docs-feedback-pigment-css
• docs-feedback-xgrid
• docs-feedback-xcharts
• docs-feedback-explore
• docs-feedback-toolpad
• docs-feedback-design-kits

Motivation

So each team can focus on its own product, without the notification noise of others.

[alexfauquette]

docs-feedback-toolpad already exist, it's just I added a "s" at feedback even if this upset native speakers 😅

Need to be a workspace owner to remove the "s"

[oliviertassinari]

Renamed