Key collisions when maxLevels is not a multiple of 8

[arnaucube]

By @ed255 in #21 (comment) :

Since you're using the ceiling here, you could find collisions when maxLevels is not a multiple of 8, and you have a len(key) == maxKeyLen where the last bits differ. Is that a problem? A quick solution I can think of is to force the maxLevels to be a multiple of 8. The other solution is to validate that the trailing bits in the key are 0.

[arnaucube]

As a note for the future: having the ability to define maxLevels not being a multiple of 8 is useful, as for example, when working with a zk-circuit, some times it can be more optimal to use 17 levels instead of 32 for a specific use case. So maybe I would go for the option of ensuring trailing bits to be 0.