Feature: Support appending an existing release

[callum-tait-pbx]

Problem
If a release already exists with the same tag then chart-releaser fails with the following error:

Error: error creating GitHub release: POST https://api.github.com/repos/my_org/actions-runner-controller-mirror/releases: 422 Validation Failed [{Resource:Release Field:tag_name Code:already_exists Message:}]

Proposed Soltuion
Check for a matching release beforehand and append to that release if the action is configured to do so.

      - name: Run chart-releaser
        uses: helm/chart-releaser-action@v1.1.0
        env:
          CR_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
          APPEND_TO_RELEASE: true

To retain compatibility make the default value false.

[terrytangyuan]

Just encountered the same issue. We have multiple charts but only some of them have version changes, which results in the already_exists error. Does anyone know any workarounds?

[qrkourier]

Releases shouldn't change, and so I'd like cr.sh to simply use the new cr --skip-existing option to ignore version collisions. If the releaser truly needs to clobber a release they could always delete them and then redeploy.