Feature request: ALB/NLB attributes parsing

[marcoreni]

While the library is able to parse ALB logs correctly, it's missing some of the attributes that are specific to ALB: https://docs.aws.amazon.com/elasticloadbalancing/latest/application/load-balancer-access-logs.html#access-log-entry-syntax

I also saw (but I'm not using it) that NLB has a different format: https://docs.aws.amazon.com/elasticloadbalancing/latest/network/load-balancer-access-logs.html#access-log-entry-format

Maybe a "load balancer type" param can be added to select which LB is being analyzed ("classic", "alb" or "nlb")?