Can support audit middleware in proxy?

[richex-cn]

Looks like the audit middleware always proxy to registry.npmjs.org now:

verdaccio/packages/plugins/audit/src/audit.ts

Line 37 in 2cee1a5

headers['host'] = 'registry.npmjs.org';

Considering having the audit middleware support the proxy option? Just like the package proxy uplink.

uplinks:
  local:
    url: http://localhost:55666/
middlewares:
  audit:
    enabled: true
    proxy: local

[mbtools]

Fork the existing audit plugin and make the necessary enhancements... or send a PR with the required changes 😃