chore: add badges to README (#44)

Author: dsanders11

README.md

@@ -1,5 +1,8 @@
 # Fiddle-Core
 
+[![CircleCI](https://circleci.com/gh/electron/fiddle-core.svg?style=svg)](https://circleci.com/gh/electron/fiddle-core)
+[![NPM](https://img.shields.io/npm/v/@electron/fiddle-core.svg?style=flat)](https://npmjs.org/package/@electron/fiddle-core)
+
 Run fiddles from anywhere, on any Electron release
 
 ## CLI