init attest action

[ejahnGithub]

Move the attest code from https://github.com/github/attestation-action

TODOs:

• packages/attest will be replaced after we have npm package for packages/attest
• add unit test

[bdehamer]

A couple of organizational changes:

• Let's NOT check-in the packages/attest/dist directory
• Move all of the files from src/helper to just the src directory
• Ditch any code that we don't need as part of this action (e.g. sbom.ts)

[bdehamer]

👍