Multi communities should have a sidebar

[dessalines]

Requirements

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Is your proposal related to a problem?

I recently removed this from lemmy-ui, since multi-communities only have the summary field.

But they should probably also have a sidebar, just like communities.

Should probably come with or after #6301

Describe the solution you'd like.

Add a sidebar to multi-community

Describe alternatives you've considered.

NA

Additional context

No response

[Nutomic]

This is not urgent, we can add new features anytime after 1.0. Moving this to 1.1 milestone to keep 1.0 focused on most urgent things. Of course its not a problem if someone implements it earlier.