Add nginx documentation about setting for fix warning of webfinger and nodeinfo.

[ynott]

This fixes nextcloud#6157.

Add a description of the settings to be added to nginx's nextcloud.conf to turn off the following warnings in nginx.

Your web server is not properly set up to resolve “/.well-known/webfinger” Your web server is not properly set up to resolve “/.well-known/nodeinfo”

[mddvul22]

How does this fix #6157 if it only addresses documentation for Nginx? This bug happens in Apache, also. Also, I don't understand how the lack of webfinger and nodeinfo well-known urls should be generating a warning, if they aren't used by any applications in a Nextcloud configuration.

[melroy89]

Hello Nextcloud people? Why not solve this Nginx documentation page regarding this issue now??