Add Helm Chart

[nabsul]

Okie doke! I think this PR is ready for a review.

In general, my goal here is to publish the simplest possible Chart. I know there were a lot of suggestions/features that I might have missed in the original design, and I'd be happy to consider adding them, either now or as a later update.

Notes:

• I started out with https://github.com/nabsul/k8s-ecr-login-renew/pull/28 as the base of this PR
• But I decided to simplify things as much as possible.
• I got rid of all the helper functions for the following reasons:
  • Trimming down long names is not a problem for our default values, and if the user wants to change them they should be responsible for using suitable values.
  • The hop from the yaml to the definition in the tpl file was annoying.
• I got rid of all pre-hooks. Everything is now defined/created inline in the main create event.
• I restructured values.yaml to make the most commonly changed values easy to access, and the less-common values a little harder to get to (nested).
• I got rid of the one-off job and instead added a NOTES.txt that gives the one-line command to kick off a manual run of the job.

While this PR is reviewed for features/correctness, I will look at the instructions to automate the publication of this Chart via github actions as described/recommended in the Helm docs.

CC: @Startouf @devec0 @armenr @xavidop @PawelLipski

[digitalrayne]

Looks good to me @nabsul - I would say you are quite the helm expert now!