add triage-labels workflow

[dbeatty10]

resolves https://github.com/dbt-labs/dbt-spark/issues/502

Group of PRs

• https://github.com/dbt-labs/dbt-snowflake/pull/519
• https://github.com/dbt-labs/dbt-bigquery/pull/601
• https://github.com/dbt-labs/dbt-spark/pull/678
• https://github.com/dbt-labs/dbt-redshift/pull/366

Checklist

• [x] I have read the contributing guide and understand what's expected of me
• [x] I have signed the CLA
• [x] I have run this code in development and it appears to resolve the stated issue
• [x] I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• [x] ~I have run changie new to create a changelog entry~ label:skip_changelog

[github-actions[bot]]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the dbt-spark contributing guide.

[github-actions[bot]]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the dbt-spark contributing guide.