Add link to Wikipedia page for cosine similarity on the cosine similarity page.

Author: kernelmethod

docs/src/similarities/cosine.md

@@ -4,7 +4,7 @@
     This section is currently being developed. If you're interested in helping write this section, feel free to [open a pull request](https://github.com/kernelmethod/LSH.jl/pulls); otherwise, please check back later.
 
 ## Definition
-*Cosine similarity*, roughly speaking, measures the angle between a pair of inputs. Two inputs are very similar if the angle between them is low, and their similarity drops as the angle between them increases.
+[Cosine similarity](https://en.wikipedia.org/wiki/Cosine_similarity), roughly speaking, measures the angle between a pair of inputs. Two inputs are very similar if the angle between them is low, and their similarity drops as the angle between them increases.
 
 Concretely, cosine similarity is computed as