feat: support Bob

[SteveLauC]

Standards checklist:

• The PR title is descriptive.
• I have read CONTRIBUTING.md
• The code compiles (cargo build)
• The code passes rustfmt (cargo fmt)
• The code passes clippy (cargo clippy)
• The code passes tests (cargo test)
• Optional: I have tested the code myself
  • I also tested that Topgrade skips the step where needed

If you developed a feature or a bug fix for someone else and you do not have the
means to test it, please tag this person here.

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Bob is a package manager for Neovim, to update installed stable and nightly versions of Neovim, run the following command:

$ bob update --all