Is it possible to use an image digest instead of a tag?

Hi, thanks for this nice chart and your Minecraft container work.

I tried to setup a server and didn't want to use an image tag instead i want to use a digest, to fix the image version.
I tried this:
```
values.yaml
image:
tag: sha256:2888e7304b837002fade0b7c939c1b2297d303d3cba891805d12c13036d8aae2
```
But the result is something like this:
```
image: itzg/minecraft-server:sha256:2888e7304b837002fade0b7c939c1b2297d303d3cba891805d12c13036d8aae2
```
Which does not work the resulting string should look like this.
```
image: itzg/minecraft-server@sha256:2888e7304b837002fade0b7c939c1b2297d303d3cba891805d12c13036d8aae2
```
[google](https://cloud.google.com/architecture/using-container-image-digests-in-kubernetes-manifests?hl=de)

Start with values.yaml and trace how the image.tag value is rendered into the container image reference. Confirm the expected digest syntax and verify that the resulting reference uses @sha256:... rather than a tag separator; the issue's example provides the completion criteria.

Written by the indexing model from the issue text.