Summary: Finds common errors in shell files. This adds the linter but does not enabled it yet.

Test Plan: N/A

Reviewers: michelle, oazizi, #engineering, philkuz

Reviewed By: #engineering, philkuz

Differential Revision: https://phab.corp.pixielabs.ai/D2310

GitOrigin-RevId: 96111281c68e7250fddddd07f0e0a92ed21e55be