Adopting NumFOCUS code of conduct

[pllim]

(I will fill in details as they come. Opening a placeholder issue for now.)

Background: We currently have only one Ombudsperson who is also a member of the Project and not a neutral party. Early 2025, after considering community feedback, the Coordination Committee decided to opt into NumFOCUS code of conduct under their "recommendations" path (i.e., their working group provides our Ombudsperson recommendations on how to resolve an incident but it is still up to us to act upon it), which would require no change to APE 0.

Status as of 2025-06-20: The Coordination Committee had a kick-off onboarding meeting with a subset of NumFOCUS code of conduct working group. We have obtained some materials (links below) and will solicit implementation feedback at the Astropy Coordination Meeting 2025.

Pros:

• We have the support of NumFOCUS code of conduct working group to handle future incidents.
• Our incident policy would be in-sync with other NumFOCUS projects that also adopted this.
• NumFOCUS policies have been fleshed out by various stakeholders and have much more details than ours.

Cons:

• We are one of the early adopters of this roll-out, so we have to be patient while NumFOCUS code of conduct working group continue to flesh out the rest of the materials.
• There is a chance NumFOCUS policies might diverge from our project philosophy in the future, though there was no such conflict at the time of writing.

Links:

• Proof-of-concept: Adopt NumFOCUS code of conduct astropy.github.com#669
• NumFOCUS onboarding materials folder (some materials are still work in progress)
• https://github.com/astropy/astropy/blob/main/CODE_OF_CONDUCT.md (links to Astropy site)
• https://github.com/astropy/.github/blob/main/CODE_OF_CONDUCT.md (links to Astropy site)
• Other mentions of code of conduct in astropy org seem to also all point to Astropy site.

Close #21

cc @astropy/coordinators @hamogu @kamila-NF