[docs] Update RELEASE.md for generating container tests for the slsa-verifier CLI

[asraa]

Describe the bug Add a description and link to it in the RELEASE.md for how to generate verifier CLI tests when publishing new builders that release the container workflow.

See https://github.com/slsa-framework/slsa-github-generator/pull/1108

See issue on creating workflows: https://github.com/slsa-framework/example-package/issues/115

To Reproduce Steps to reproduce the behavior:

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2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior A clear and concise description of what you expected to happen.

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Additional context Add any other context about the problem here.