Add something to check that secrets aren't being checked in

[coretl]

As a pre-commit hook.

Something like this:
https://github.com/Yelp/detect-secrets

[coretl]

From the readme:

We recommend setting this up as a pre-commit hook. One way to do this is by using the pre-commit framework:

# .pre-commit-config.yaml
repos:
-   repo: https://github.com/Yelp/detect-secrets
    rev: v1.4.0
    hooks:
    -   id: detect-secrets
        args: ['--baseline', '.secrets.baseline']
        exclude: package.lock.json