Related Linear issue [[ https://linear.app/comm/issue/ENG-1435/add-shellcheck-to-lint-staged | here ]]. Adds a task for handling `*.sh` staged files and runs the same ShellCheck command we use in Buildkite/GitHub Actions. Because this we're running ShellCheck in the pre-commit stage, issues with shell scripts will be surfaced to developers earlier, which is ideal.
Depends on D4771 because the user needs [[ https://www.shellcheck.net/ | ShellCheck ]] installed locally.
Also depends on D4770 (related issue: [[ https://linear.app/comm/issue/ENG-1435/add-shellcheck-to-lint-staged | ENG-1568 ]]) since developers using the Nix shell also need access to ShellCheck.