sd: Install man page and shell completions

[cypher]

• Have you followed the guidelines for contributing?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with brew install --build-from-source <formula>, where <formula> is the name of the formula you're submitting?
• Is your test running fine brew test <formula>, where <formula> is the name of the formula you're submitting?
• Does your build pass brew audit --strict <formula> (after doing brew install <formula>)?

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Also install sd's man page and shell completions for bash and zsh, similar to how the ripgrep formula does.

[chenrui333]

Thanks @cypher!!