Functions to compute L1 distance

[MBkkt]

Manhattan distance sometimes useful

https://github.com/google-research/google-research/tree/master/scann/scann/distance_measures/one_to_one
https://github.com/ydb-platform/ydb/tree/main/library/cpp/l1_distance

Already done for bit (hamming)

[ashvardanian]

This might be interesting for i8 inputs and any other low-capacity integral types, and might be related to #100 for sparse distances

[raulod]

l1 is picking momentum is many high dimensional usage where l2 distances are unstable.

[ashvardanian]

It seems like L1 is still very niche and L2 & Angular distances are mostly used.

Would be great to see some more user requests before switching the attention from matrix multiplications.