Wrapper chart is missing from package-images.yaml

Feature Request

Include Wrapper chart version in the release's package-images.yaml artifact.

Why

While there are no images in the wrapper chart, it is still beneficial to have the version of the chart in this release artifact in order to determine what version of the chart is included with the release.

Proposed Solution

Include a section in this file for the wrapper and have the list of images empty

  wrapper:
    version: "0.4.1"
    images: []

This would allow someone to determine what version of the wrapper chart (and any other chart) is required programmatically without checking out the commit associated with the release and parsing the chart values.