feat(ci): Add Scorecard workflow

[AdamKorcz]

This PR adds the Scorecard action to Trainers’s CI.

Scorecard is a tool that scans for a number of supply-chain threats and assesses whether Trainer mitigates these threats. Running Scorecard allows projects to avoid degradation in its development pipeline, ie. the action continuously monitors for all Scorecards heuristics and alerts if a given PR increases the risk of a given threat. Projects can also add a badge to demonstrate their Scorecard score.

I highly recommend enabling the “Branch-Protection” check which is disabled in this PR, however, for instructions on enabling it, see the workflow.
Checklist:

• Docs included if any changes are user facing

[google-oss-prow]

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[coveralls]

Pull Request Test Coverage Report for Build 17587861526

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 52.136%

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Totals
Change from base Build 17582427745:	0.0%
Covered Lines:	1025
Relevant Lines:	1966

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💛 - Coveralls