✨ Add LMPOP

[JerrodCarpenter]

• Adding LMPOP
• https://github.com/redis/redis-rb/issues/1187

➜  redis-rb git:(lmpop) ./bin/console 
irb(main):001:0> redis = Redis.new(url: "redis://localhost:6379/2")
=> #<Redis client v5.0.6 for redis://localhost:6379/2>
irb(main):002:0> redis.rpush("list", [6, 1, 2, 3, 4, 5, 6])
=> 8
irb(main):003:0> redis.lmpop("list")
=> ["list", ["6"]]
irb(main):004:0> redis.lmpop("list", modifier: "RIGHT")
=> ["list", ["6"]]
irb(main):005:0> redis.lmpop("list", modifier: "RIGHT", count: 2)
=> ["list", ["5", "4"]]