Add support for QUIC and HTTP/3

[gstrauss]

Is there any plan to add support for HTTP/3 since it is now supported in all major browsers?

(cloned from mozilla/ssl-config-generator#230)

[Lordfirespeed]

For nginx specifically, I have found a somewhat elegant way of doing http3 but it requires an extra file.

See catch-all.nginxconf

A 'catch-all' aka fallback server block is a natural place to put the necessary reuseport directive.

Then e.g. https://github.com/ducompsoc/durhack-nginx/blob/main/production/%5Bapi.durhack.com%5D.nginxconf is an example of a server block which listens on both http2 and http3