Update RocksDB blog authors

Summary:
Adding my name to the authors list so that I can publish a post to rocksdb blog (rocksdb.org).
Closes https://github.com/facebook/rocksdb/pull/2379

Differential Revision: D5143582

Pulled By: sagar0

fbshipit-source-id: d85163f8b59aaeb07ac2a1cdd776ae335c7062b9

docs/_data/authors.yml

@@ -52,3 +52,7 @@ IslamAbdelRahman:
 ajkr:
   full_name: Andrew Kryczka
   fbid: 100010829806660
+
+sagar0:
+  full_name: Sagar Vemuri
+  fbid: 2419111