Add skip-packaging option

[gmorse81]

after reading through the PRs and issues on this project, it seems there are a number of requests for more custom packaging. These include things like tagging the chart based on git tags or just supporting the option to trigger on tag. I was, too, running into an issue like this.

my specific issue is that I wanted to be able to tag a commit and have the chart packaged with that tag for the chart version and the app version.

but... I think that all of these specific packaging options are going to be difficult to maintain over time, so I propose another solution. Add a variable to "skip-packaging". this option would skip the packaging altogether and allow the user to do their own custom packaging in an earlier step.

I have made the modifications to this project to allow for this and will submit a PR shortly after I get the docs updated.