Update README

Added build instructions

Author: danesparza

README.md

@@ -1,2 +1,11 @@
 # centralconfig-ui [![Circle CI](https://circleci.com/gh/cagedtornado/centralconfig-ui.svg?style=shield)](https://circleci.com/gh/cagedtornado/centralconfig-ui)
 UI for the [centralconfig service](https://github.com/cagedtornado/centralconfig)
+
+## Building
+
+Make sure [yarn](https://yarnpkg.com/en/) is installed, then:
+
+```shell
+yarn
+yarn build
+```