USWDS-Compile: Create add-issue-labels workflow

[amyleadem]

Summary

Note:
This action will also be added to every USWDS repo that adds issues to the project board.

Added a workflow that creates a "Status: Triage" label on all new issue submissions.

More information about the action: github-script action

Breaking change

This is not a breaking change.

Related issue

Closes #63

Related pull requests

No changelog is required for this update.

Preview link

Preview link: N/A

Problem statement

All new USWDS project issues should receive the "Status: Triage" label when opened. This label is important because we sort through items with this label in the project Triage tab during issue triage. However, the "Status: Triage" label is currently only added to issues created via our bug or feature request templates.

Solution

Creating a workflow that applies the "Status: Triage" label to all newly opened issue will ensure that all new issues are added to the project triage tab.

Testing and review

To test:

1. Open a new blank issue in this test repo.
2. Confirm that the issue receives the "Status: Triage" label (This might take a minute to complete)
3. Confirm that the add labels action file in this PR matches the one in the demo repo
4. Confirm that this action is a reasonable addition.

[mahoneycm]

GH action yml file matches test repo 👍

[mejiaj]

Nice job! I was able to go to the test repo and use the enhancement template to create an issue. The correct labels showed up.