Add RUN_ATTEMPT to @actions/github Context class

[sshmaxime]

This PR add GITHUB_RUN_ATTEMPT to @actions/github Context class.

I need to retrieve the RUN_ATTEMPT variable in order to retrieve some informations from my jobs using Octokit, like so:

 const jobs = await octokit.paginate(octokit.rest.actions.listJobsForWorkflowRunAttempt, {
    owner: github.context.repo.owner,
    repo: github.context.repo.repo,
    run_id: github.context.runId,
    attempt_number: github.context.runAttempt, // Missing :'(
  });

[TingluoHuang]

@sshmaxime do you mind fix those linter error? 🙇

[sshmaxime]

@TingluoHuang Done 🙏

[sshmaxime]

@TingluoHuang Thank you for your fast review and merge 🙏 Do you think you'll publish asap to npm ?

[TingluoHuang]

@sshmaxime i might not have permission to publish one. 😢

[sshmaxime]

Oh that's really sad. Who should I contact, if any @TingluoHuang ? 🙏