CORS

[BeroBurny]

After using a Nimbus beacon node find out that the server does not send CORS header

This header should be present and configurable via params (like the user can add some address to the CORS list).

[AuHau]

To add to that, CORS is not only about "allowing origin", but the browser is doing preflight request check using OPTION request, where it also check for for allowed headers and methods. These are currently not possible to configure using presto.

We had to implement our own OPTION endpoint just to make CORS work: codex-storage/nim-codex#869

IMHO this should be handled on the framework level.