Support the org-level `Skillset` field in sync-issue-fields

[ericgodwin]

Summary

sync-issue-fields currently copies an issue form's type and scope dropdown answers onto the repo-level issue type and the OvertureMaps org-level Scope field (ID 44814929). The org has since added a Skillset field (ID 45229885, "What is the primary skill needed to complete this task?", options: data analysis, data science, dev ops, engineering). Issues opened from a form with a Skillset dropdown still require manual triage to set it.

Proposed change

Extend the action so a skillset form answer is written to the org-level Skillset field with the same semantics already used for Scope:

• New inputs: skillset-form-field (default skillset) and skillset-org-field-id (default 45229885).
• Include Skillset in the existing single PATCH /repos/{owner}/{repo}/issues/{issue_number} call — issue_field_values already accepts multiple {field_id, value} entries, so no extra API round trip.
• Preserve existing behavior: skip if the field is already set (don't clobber manual triage), skip entirely if no recognized form answers are present, and keep the try/catch warning for 422s from unexpected values.
• Update the "Determine desired updates" step so the skillset answer short-circuits alongside type/scope, leaving the no-op path unchanged for issues not created from a matching template.

Open question

The current design hardcodes one org field via scope-org-field-id. Adding a second field this way works but doesn't scale. An alternative is a single org-fields input taking a JSON/YAML map of form field id → org field id, which would make future fields config-only. Worth deciding before implementing.

Acceptance criteria

• An issue opened from a form with type, scope, and skillset answers has all three set automatically.
• A Skillset value already set before the action runs is not overwritten.
• Issues without a skillset answer behave exactly as they do today.
• README.md documents the new input(s), defaults, and how to find the field ID.