Automatically label and close stale issues

[colekettler]

We should use GitHub Actions to automatically label and close out issues that are not actionable or otherwise haven't been prioritized. The stale action is ideal for this.

The length of time before an action is considered stale is configurable. I think that a good starting point for this project would be 60 days until stale and a further 7 until close, the default settings. We typically create issues in response to Django upgrades being available and address those quickly. Other enhancement requests that are not prioritized within that time period are not likely to be prioritized later.