Include SHA256 and other Hashes in Release as Separate File (e.g. sha256sums File)

It would be good to include `sha256sum` Values and other Hashes as Part of the Release Package in the form of a Separate File (e.g. as `sha256sums.txt`), besides being described in the Release Notes.

The purpose would be automatic CI/CD in Case somebody wants to build (like I intend to) a Docker Container automatically).

Alternatively one can use the GitHub API and fetch the Assets sha256 sums from there, e.g.:

* https://api.github.com/repos/aptible/supercronic/releases/latest
* https://api.github.com/repos/aptible/supercronic/releases/tags/v0.2.46

Then it can be used in your Automation as:
```
curl --silent https://api.github.com/repos/aptible/supercronic/releases/latest | jq -r '.assets[]? | select(.name == "supercronic-linux-amd64") | .digest'
```

or
```
curl --silent https://api.github.com/repos/aptible/supercronic/releases/tags/v0.2.46 | jq -r '.assets[]? | select(.name == "supercronic-linux-amd64") | .digest'
```

It would also be good to have an official Docker Image with some Variations (alpine,debian,distroless).

Start by reviewing the GitHub release assets and API endpoints linked in the issue, along with the existing release process. Define the checksum file contents and naming from the current release artifacts, then verify that a release exposes the file and that its hashes can support the shown curl and jq automation.

Written by the indexing model from the issue text.