Add documentdation on getSimilarity API function

Change-Id: If4dd30c78960a9d49ac55ea48897bd9e7f84118c
diff --git a/README.md b/README.md
index 06c8a06..ea47979 100644
--- a/README.md
+++ b/README.md
@@ -55,6 +55,7 @@
 | ----------- | ----------- | ----------- |
 | / | word, n, dedupe, cutoff, json=1 | get paradigmatic and syntagmatic neighbours, from word embeddings |
 | getCollocationAssociation | w, c       | get association scores for specific node collocate pairs |
+| getSimilarity             | w1, w2     | get cosine similarity of w1 and w2 |
 
 ### Get classical (count-based) collocates