User should be able to star DMs, channels for top placement

[holmesworcester]

Users may have a long list of channels or DMs. Users should be able to star channels or DMs.

Starred channels and DMs should be synced across the user's devices, and should display in a "Starred" category with other starred items.

[holmesworcester]

See also: https://github.com/TryQuiet/quiet/issues/2430

[jgaylor]

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