More dashboard metrics

[dcherian]

See https://devstats.scientific-python.org/index.html

Looking at numpy, I like the

1. lifetime of issues
2. pony factor
3. PR lifetime
4. Number of PR participants

These seem like nice things to add to our dashboard

[andersy005]

we could also use the official GitHub Action: https://github.com/github/issue-metrics for pulling statistics around issues, discussions and PRs like:

• Avg time to close
• Avg time to first response
• Avg time to answer (for discussions)