Secret detection hook

[chgrv]

We should consider adding a precommit hook for preventing accidental inclusion of secrets. There are several options here, a few examples:

• https://github.com/awslabs/git-secrets - simple regexes, requires manual configuration and definition of regexes
• https://trufflesecurity.com/trufflehog - more advanced, wider scope than just the precommit hook

The scope of the issue includes adding the hook and setting it up, including any necessary configuration of f.x. regexes.