docs: update local env setup info

Author: jamesgeorge007

CONTRIBUTING.md

@@ -4,6 +4,6 @@
 - Clone the repository locally.
 - Make your changes to the code.
 - Run `npm install`.
-- Run `npm link` to install docsify cli in to global.
+- Run `npm link` which creates a symlink and thereby `docsify` can be accessed globally.
 - Commit your changes with a message following the [`conventional-changelog-angular` commit message convention](https://github.com/conventional-changelog/conventional-changelog/blob/master/packages/conventional-changelog-angular/convention.md).
 - Push to Github and open a pull request.