Add PR Welcone to README.md

Author: MrBrown6210

README.md

@@ -1,6 +1,9 @@
-
 <h1 align="center">Express Typescript Mongoose Boilerplate</h1>
+
 <p align="center">
+  <a href="http://makeapullrequest.com">
+    <img src="https://img.shields.io/badge/PRs-welcome-brightgreen.svg?style=flat-square" alt="PR" />
+  </a><br>
   A boilerplate/starter project for quickly building RESTful APIs using Node.js, Express, and Mongoose.
 </p>
 The app comes with many built-in features, such as authentication using JWT, request validation, unit and integration tests, etc.