Add Private Network Check

[issackelly]

Google is starting to ship checks for Private Networks[1]. This is causing me to make some adjustments to my site and I figured I'd start down the path of a PR.

[1] https://developer.chrome.com/blog/private-network-access-preflight/

[adamchainz]

Thanks for this. First time I've heard of this feature!

After skimming the spec, it looks like one should only respond with Access-Control-Allow-Private-Network if Access-Control-Request-Private-Network is present in the request. Could you make that change? Also please add a release note.

[adamchainz]

as above

[issackelly]

of course. thanks for the quick response. I will try to make this change shortly.

[flaper87]

@issackelly any chance you have some time to address @adamchainz feedback? 🙏

[untidy-hair]

Hi, can this be merged soon? Thanks everyone.

[adamchainz]

Superceded by #833, which has been merged with co-authored-by for you @issackelly . Thanks for your work.