Implement cosine similarity and cosinepair (#327)

* Implement cosine similarity and cosinepair

src/metrics/distance/mod.rs

@@ -13,6 +13,8 @@
 //! <script src="https://polyfill.io/v3/polyfill.min.js?features=es6"></script>
 //! <script id="MathJax-script" async src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js"></script>
 
+/// Cosine distance
+pub mod cosine;
 /// Euclidean Distance is the straight-line distance between two points in Euclidean spacere that presents the shortest distance between these points.
 pub mod euclidian;
 /// Hamming Distance between two strings is the number of positions at which the corresponding symbols are different.