Run shellcheck on bash file

[yuvipanda]

Ref #64

[yuvipanda]

shellcheck doesn't support zsh unfortunately

[ellie]

shellcheck doesn't support zsh unfortunately

that's a shame!

Thank you for this one 🚀

[ismith]

Shellcheck claims to support zsh, or at least https://github.com/ludeeus/action-shellcheck includes it in their list of suffixes - I'll take a pass at it.

[ismith]

... I stand corrected :sadpanda:

In src/shell/atuin.zsh line 1:
#!/bin/zsh
^-- SC1071: ShellCheck only supports sh/bash/dash/ksh scripts. Sorry!

(Shellcheck will run on the file if it lacks a shellbang, but ... I guess it's assuming it's bash? So I'm going to exclude it from files checked by the shellcheck action.)