docs(badges): add license badge

Author: felixfbecker

README.md

@@ -9,6 +9,7 @@
 [![Dependencies](https://david-dm.org/sourcegraph/javascript-typescript-langserver.svg)](https://david-dm.org/sourcegraph/javascript-typescript-langserver)
 [![semantic-release](https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg)](https://github.com/semantic-release/semantic-release)
 [![OpenTracing Badge](https://img.shields.io/badge/OpenTracing-enabled-blue.svg)](http://opentracing.io)
+[![License](https://img.shields.io/github/license/sourcegraph/javascript-typescript-langserver.svg)]()
 [![Gitter](https://badges.gitter.im/sourcegraph/javascript-typescript-langserver.svg)](https://gitter.im/sourcegraph/javascript-typescript-langserver?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
 
 This is a language server for JavaScript and TypeScript that adheres to the [Language Server Protocol (LSP)](https://github.com/Microsoft/language-server-protocol/blob/master/protocol.md). It uses [TypeScript's](http://www.typescriptlang.org/) LanguageService to perform source code analysis.