docs(readme): fix dead link lerna website (#2216)

CONTRIBUTING.md

@@ -28,7 +28,7 @@ We configured the tslint extension to run on save in or [vscode workspace](#vsco
 
 ## Runner Stryker locally
 
-We use [Lerna](https://lernajs.io/) to manage the packages in this repository. You don't have to install it globally. The packages themselves can be found in the [packages folder](https://github.com/stryker-mutator/stryker/tree/master/packages). Commands such as `npm test` can be executed from the root of the project but executing them inside of a package folder is more time efficient. However, we suggest running `npm test` in the root of the project before a commit to ensure that everything still works. To get Stryker running locally, please follow these steps:
+We use [Lerna](https://lerna.js.org/) to manage the packages in this repository. You don't have to install it globally. The packages themselves can be found in the [packages folder](https://github.com/stryker-mutator/stryker/tree/master/packages). Commands such as `npm test` can be executed from the root of the project but executing them inside of a package folder is more time efficient. However, we suggest running `npm test` in the root of the project before a commit to ensure that everything still works. To get Stryker running locally, please follow these steps:
 
 1. Clone the repository
 1. Install dependencies using `npm install` in the root of the project