Update README.md

Just Adding the npm install in the docs.
To avoid people to have to search trough the issues to see for the exact line for npm install.

Author: FrancescoMussi

README.md

@@ -33,7 +33,8 @@ If you're looking for v1 check this [branch](https://github.com/apertureless/vue
 
 ## Install
 
-Simply run `yarn add vue-chartjs chart.js`
+Yarn install: `yarn add vue-chartjs chart.js`
+Npm install: `npm install vue-chartjs chartjs --save`
 
 Or if you want to use it directly in the browser add