Accept any iterator type as trie leaves

[dennis-tra]

I could imagine that the ergonomics of the API (at least in my use case :D) would be improved if one could just add a byte type instead of a string of bits as leave nodes. Internally, you could use a library like https://pypi.org/project/bitarray/ to transform the bytes to a bitarray to build the prefix trie. The library seems to have C-bindings which indicates (not guarantees) performance benefits compared to the string conversion of bytes to bitstrings. Maybe the add function signature could accept anything that's a python iterator instead of restricting it to strings?