Update README.md (#200)

Added security contact

Author: aalavandhan

README.md

@@ -6,6 +6,8 @@ SPOT is an inflation-resistant store of value fully collateralized by AMPL backe
 
 [![Nightly](https://github.com/ampleforth/spot/actions/workflows/nightly.yml/badge.svg)](https://github.com/ampleforth/spot/actions/workflows/nightly.yml)  [![Coverage Status](https://coveralls.io/repos/github/ampleforth/spot/badge.svg?branch=main)](https://coveralls.io/github/ampleforth/spot?branch=main)
 
+Security contact: [dev-support@ampleforth.org](mailto:dev-support@ampleforth.org)
+
 
 ### Package organization