Cannot recover from failure scenario where the release was published in GH but index.yaml isn't updated

If for some reason the process of releasing a chart ends up in failure, changes might not be detected when rerunning the release action.

**Scenario used to reproduce the problem**: protected `gh-pages` branch

1. Protect your `gh-pages` branch to only allow code to be merged from PRs with reviews.
2. Push a chart update.
3. The Github Release with the archive files will be published.
4. The release action will fail on the push to `gh-pages` due to the protection configuration.
5. Remove branch protection from `gh-pages`.
6. Rerun the release action.

**Outcome**: it won't detect changes due to the presence of the the release and tag for the chart.

**Workaround**: manually delete the Github release and tag, then rerun the release action.

**Expected outcome**: the action detects that even though the Github release and tags are present, but my `index.yaml` file still needs to be updated. So it proceeds to update it and push the commit to `gh-pages`.

This currently happens with the latest release of this chart and chart-releaser (both on 1.2.1).

Start by tracing the release action and its interaction with chart-releaser when a GitHub Release and tag already exist but index.yaml was not updated. Reproduce the protected gh-pages scenario, then rerun after removing protection. Done means the rerun detects the missing index.yaml update and pushes the required commit without deleting the release or tag.

Written by the indexing model from the issue text.