Add CORS server option

[nedjs]

Allow an optional setting CORS header. Thinking something like --access-origin *

Alternatively just allow the setting of a header: --header "Access-Control-Allow-Origin: *"

https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS

[SimplGy]

Great idea!

Maybe allowing headers to be set in the general case is most useful?

If you do the work I'll take the CR.

I think there's a library that turns a json object into a header string, not sure what that looks like. Or just letting people set it as a free text string, whatever feels right to you.