Feature request: Package "environment" credential helper

[TobiX]

The kaniko image already contains some credential helpers, would it be possible to also ship something like https://github.com/isometry/docker-credential-env? This would help in using Kaniko in CI/CD pipelines, since the use won't have to write a JSON config file via crude shell scripting.

(If you think this is out-of-scope for kaniko, feel free to close this issue)