superfile: add pinnded folder and first use option

[rhoriguchi]

Description

Code can be found here.

• Add an option to configure the pinned directories that get shown on the left panel
• Add an option to disable the first-use pop-up

Checklist

• Change is backwards compatible.

• Code formatted with nix fmt or
  nix-shell -p treefmt nixfmt deadnix keep-sorted --run treefmt.

• Code tested through nix run .#tests -- test-all or
  nix-shell --pure tests -A run.all.

• Test cases updated/added. See example.

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  {long description}
  

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  • Basic tests added. See Tests

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[rycee]

Thanks for the contribution! Please make sure the commit message follows the contribution guidelines, specifically the subject should be at most around 50 character long.