Add nginx config example to README

[Matheus Fillipe]

Very nice project!
Solution for #17 and might be nice in case someone else wants to know:

location /music/ {
    proxy_pass_header  Set-Cookie;
    proxy_set_header   Host               $host;
    proxy_set_header   X-Real-IP          $remote_addr;
    proxy_set_header   X-Forwarded-Proto  $scheme;
    proxy_set_header   X-Forwarded-For    $proxy_add_x_forwarded_for;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "Upgrade";
    proxy_set_header Host $host;
    proxy_pass http://localhost:8080/;
  }

[Ondřej Žára]

Thanks @matheusfillipe ! I added that to README in 148d215