Add list parsers command

[iBug]

$ ./ayano list parsers
NAME            DESCRIPTION                                    
caddy-json      Caddy's default JSON format                     
goaccess        GoAccess output format                          
nginx-combined  For nginx's default `combined` format           
nginx-json      `nginx-json` format, see README.md for details  

$ ./ayano list parsers --all
NAME            DESCRIPTION                                    
caddy           An alias for `caddy-json`                       
caddy-json      Caddy's default JSON format                     
combined        An alias for `nginx-combined`                   
goaccess        GoAccess output format                          
nginx-combined  For nginx's default `combined` format           
nginx-json      `nginx-json` format, see README.md for details  
ngx_json        An alias for `nginx-json`