Increments the number stored at field in the hash stored at key by
increment. If key does not exist, a new key holding a hash is created. If
field does not exist the value is set to 0 before the operation is
performed.
The range of values supported by HINCRBY is limited to 64 bit signed
integers.
@return
@integer-reply: the value at field after the increment operation.
@examples
Since the increment argument is signed, both increment and decrement
operations can be performed:
@cli
HSET myhash field 5
HINCRBY myhash field 1
HINCRBY myhash field -1
HINCRBY myhash field -10