### Description of the change
This PR is a continuation of the work done by @dgershman in [534](https://gitea.com/gitea/helm-chart/pulls/534), to allow users to override the image from the default rootless behavior of appending `-rootless` to the end of the image tag.
### Benefits
Allows more flexibility to use externally maintained images that are rootless but don't follow the `-rootless` tag convention.
### Applicable issues
- fixes#532
### Additional information
No breaking changes. This does not affect the `image.rootless` conditional checks or the current behavior if someone still wants to rely on the chart to append `-rootless`.
### Checklist
- [x] Parameters are documented in the `values.yaml` and added to the `README.md` using [readme-generator-for-helm](https://github.com/bitnami-labs/readme-generator-for-helm)
- [x] Breaking changes are documented in the `README.md`
- [x] Templating unittests are added
Co-authored-by: TristanHoladay <[email protected]>
Co-authored-by: pat-s <[email protected]>
Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/550
Reviewed-by: justusbunsi <[email protected]>
Reviewed-by: pat-s <[email protected]>
Co-authored-by: TristanHoladay <[email protected]>
Co-committed-by: TristanHoladay <[email protected]>
