httpcaddyfile: Allow php_fastcgi to be used in route directive
httpcaddyfile: Allow php_fastcgi to be used in route directive

Fixes
https://caddy.community/t/v2-help-to-set-up-a-yourls-instance/7260/22

abiosoft/caddy,abiosoft/caddy,mholt/caddy,l3dlp/caddy,mholt/caddy,l3dlp/caddy,l3dlp/caddy