docs: adds dependabot badge

Author: huafu

README.md

@@ -1,4 +1,4 @@
-# ts-jest [![npm version](https://badge.fury.io/js/ts-jest.svg)](https://badge.fury.io/js/ts-jest) [![NPM downloads](https://img.shields.io/npm/dm/ts-jest.svg?style=flat)](https://npmjs.org/package/ts-jest) [![Known Vulnerabilities](https://snyk.io/test/github/kulshekhar/ts-jest/badge.svg)](https://snyk.io/test/github/kulshekhar/ts-jest) [![Coverage Status](https://coveralls.io/repos/github/kulshekhar/ts-jest/badge.svg?branch=master)](https://coveralls.io/github/kulshekhar/ts-jest?branch=master) [![Build Status for linux](https://travis-ci.org/kulshekhar/ts-jest.svg?branch=master)](https://travis-ci.org/kulshekhar/ts-jest) [![Build Status for Windows](https://ci.appveyor.com/api/projects/status/g8tt9qd7usv0tolb/branch/master?svg=true)](https://ci.appveyor.com/project/kulshekhar/ts-jest/branch/master)
+# ts-jest [![npm version](https://badge.fury.io/js/ts-jest.svg)](https://badge.fury.io/js/ts-jest) [![NPM downloads](https://img.shields.io/npm/dm/ts-jest.svg?style=flat)](https://npmjs.org/package/ts-jest) [![Known Vulnerabilities](https://snyk.io/test/github/kulshekhar/ts-jest/badge.svg)](https://snyk.io/test/github/kulshekhar/ts-jest) [![Coverage Status](https://coveralls.io/repos/github/kulshekhar/ts-jest/badge.svg?branch=master)](https://coveralls.io/github/kulshekhar/ts-jest?branch=master) [![Dependabot Status](https://api.dependabot.com/badges/status?host=github&repo=kulshekhar/ts-jest)](https://dependabot.com) [![Build Status for linux](https://travis-ci.org/kulshekhar/ts-jest.svg?branch=master)](https://travis-ci.org/kulshekhar/ts-jest) [![Build Status for Windows](https://ci.appveyor.com/api/projects/status/g8tt9qd7usv0tolb/branch/master?svg=true)](https://ci.appveyor.com/project/kulshekhar/ts-jest/branch/master)
 
 <img src="./icon.png" align="right" title="ts-jest Logo" width="128" height="128">