Support CORS policy for requests

[arrake0101]

Because websites need to be separated from the front end, cross-domain access requests are required.
After the merge, pelease redistribute a version and redeploy it.
Thank you.

[arrake0101]

I have developed hacd.fun, welcome to visit.

[jojoin]

There are multiple considerations here:

1. Adding a generic Header will increase the load on network requests, especially if Hacash is used as a large-scale data service in the future.
2. some third-party services may not want their back-end data to be called by other front-ends (e.g. to save on traffic charges).
3. If you need your own node service to be cross-domain, you can add any desired Header via the Nginx proxy.
   The preference here is to keep the CORS policy unadded, is there more to consider?

[arrake0101]

I think proxy requests consume extra traffic, which is unnecessary.
Later, I consider loading this item through the configuration file.