chore: Add Shellcheck commands GitHub Actions

[masamallow]

Description

Add Shellcheck GitHub Actions, because of Raycast official recommendation.

we highly recommend using the Shellcheck linter as this will ensure smooth running of your script. All scripts uploaded to GitHub will need to have been run through ShellCheck.

See: raycast/script-commands>README>Create your own Script Commands

• This PR only supports the commands directory scope.
• Existing .sh files have already been validated.

FYI

• https://github.com/koalaman/shellcheck
• ShellCheck: Recursiveness

Type of change

• Other (Add GitHub Actions)