Add Xor Filters

[Callidon]

As pointed in #8 we can add Xor Filters to the library

See https://lemire.me/blog/2019/12/19/xor-filters-faster-and-smaller-than-bloom-filters/ for more details

[folkvir]

For copyright, there exists one C-header only impl: https://github.com/FastFilter/xor_singleheader
A pure-python impl as well as a binding could be possible.

[folkvir]

Just for references, the official accepted paper :

• Graf, Thomas Mueller, and Daniel Lemire. "Xor filters: Faster and smaller than bloom and cuckoo filters." Journal of Experimental Algorithmics (JEA) 25 (2020): 1-16.
• full article
• Official github of the author https://github.com/FastFilter/xorfilter

[folkvir]

integrated in develop, will be pushed in v2.0.0