Add support for GT and LT in ZADD

[chorin1]

Expected Behavior

Since Redis 6.2 ZADD has additional useful options - LT (less than) and GT (greater than).
There should be corresponding functions in go-redis -> ZAddLT & ZAddGT.

Possible Implementation

Since GT, LT and NX options are mutually exclusive there are two ways to go from here:

1. Add ZAddLT/GT + ZIncrGT/LT + ZAddXXGT/LT (total of 6 functions)
2. Have a single ZAdd function and introduce a Zadd options struct => breaking change.

[chorin1]

If there's interest, I can cook up a PR

[monkey92t]

We can keep the more commonly used API, such as:
zadd key score member...
zaddNX..

In addition, we can add an API that supports all parameters, such as ZAddArgs(ctx, key, *ZAddArgs)
What do you think?

[vmihailenco]

+1 to ZAddArgs(ctx, key, ZAddArgs) (not a *ZAddArgs since it is a small struct)

[monkey92t]

@chorin1 HI~
I am currently upgrading the sorted set series of commands. If you have no plans at this time, I will modify the ZADD command

[chorin1]

@monkey92t go ahead.
I saw that you already transitioned the item to "in-progress" so I didn't start any work on my end.
LMK if you need help.