README: Add Travis badge

Author: Kocal

README.md

@@ -1,5 +1,7 @@
 # vue-web-extension-boilerplate
 
+[![Build Status](https://travis-ci.org/Kocal/vue-web-extension.svg?branch=master)](https://travis-ci.org/Kocal/vue-web-extension)
+
 This template allows you to quickly start a web extension containing:
 
 - Boilerplate for `manifest.json` and `background.js` files, and for `icons` / `popup` folders,
@@ -45,4 +47,4 @@ Watch for modifications then run `npm run build:web`.
 ### `npm run build-zip`
 
 Build a zip file following this format `<name>-v<version>.zip`, by reading `name` and `version` from `manifest.json` file.
-Zip file is located in `dist-zip` folder.
+Zip file is located in `dist-zip` folder.