Add quic/http3 sandbox

[phlax]

discussing with @nguyenptk which sandboxes would be most useful to add - the possibility of adding an http3 sandbox came up - which seems like a good idea

[phlax]

cc @alyssawilk @RyanTheOptimist

[nguyenptk]

hi - could you guys share some information or where should I start first?

[phlax]

if you check in the configs/ directory there are some example configs there

[github-actions]

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