fabric: add shell completions

[jaredmontoya]

Things done

Adds shell completions closes #470097

• Built on platform:
  • [x] x86_64-linux
  • [ ] aarch64-linux
  • [ ] x86_64-darwin
  • [ ] aarch64-darwin
• Tested, as applicable:
  • [ ] NixOS tests in nixos/tests.
  • [ ] Package tests at passthru.tests.
  • [ ] Tests in lib/tests or pkgs/test for functions and "core" functionality.
• [ ] Ran nixpkgs-review on this PR. See nixpkgs-review usage.
• [x] Tested basic functionality of all binary files, usually in ./result/bin/.
• Nixpkgs Release Notes
  • [ ] Package update: when the change is major or breaking.
• NixOS Release Notes
  • [ ] Module addition: when adding a new NixOS module.
  • [ ] Module update: when the change is significant.
• [x] Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other READMEs.

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[ethancedwards8]

nixpkgs-review result

Generated using nixpkgs-review.

Command: nixpkgs-review pr 470537 Commit: c7042f1ce1585bbff0e8ef806aa17c76b0c735c9

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aarch64-darwin

:white_check_mark: 1 package built:

• fabric-ai

[jaredmontoya]

@NixOS/nixpkgs-merge-bot merge

[nixpkgs-ci[bot]]

@jaredmontoya wants to merge this PR.

Requirements to merge this PR with @NixOS/nixpkgs-merge-bot merge:

• :white_check_mark: PR targets a development branch.
• :white_check_mark: PR touches only files of packages in pkgs/by-name/.
• :x: PR is at least one of:
  • :white_large_square: Approved by a committer.
  • :white_large_square: Backported via label.
  • :white_large_square: Opened by a committer.
  • :white_large_square: Opened by r-ryantm.
• :white_check_mark: jaredmontoya is a member of @NixOS/nixpkgs-maintainers.
• :white_check_mark: jaredmontoya is a maintainer of all touched packages.

:x: Pull Request could not be merged (#305350)