Fixes#126
Add option to suppress job summary and provide attestation URL output.
* Add `suppress-summary` input parameter to `action.yml` to control job summary suppression.
* Add `attestation-url` output parameter to `action.yml` to provide attestation URL.
* Import `getInput` and `setOutput` functions from `@actions/core` in `src/main.ts`.
* Check `suppress-summary` input value and conditionally skip summary generation in `src/main.ts`.
* Set `attestation-url` output with generated attestation URL in `src/main.ts`.
* Add `generateAttestationUrl` and `generateSummary` functions in `src/main.ts`.
* Update tests in `__tests__/main.test.ts` to cover `suppress-summary` input and verify `attestation-url` output.
* Add test for JSON output format for multiple attestations in `__tests__/main.test.ts`.
---
For more details, open the [Copilot Workspace session](https://copilot-workspace.githubnext.com/actions/attest-build-provenance/issues/126?shareId=XXXX-XXXX-XXXX-XXXX).
