Fixing CLI snippets in quick start (graphprotocol#526)

* Fixing CLI snippet

* adding colons

Author: MichaelMacaulay

website/pages/en/quick-start.mdx

@@ -24,12 +24,16 @@ The Graph CLI is written in JavaScript and you will need to have either `npm` or
 
 On your local machine, run one of the following commands:
 
+Using [npm](https://www.npmjs.com/):
+
 ```sh
-# NPM
-$ npm install -g @graphprotocol/graph-cli
+npm install -g @graphprotocol/graph-cli
+```
 
-# Yarn
-$ yarn global add @graphprotocol/graph-cli
+Using [yarn](https://yarnpkg.com/):
+
+```sh
+yarn global add @graphprotocol/graph-cli
 ```
 
 ## 3. Initialize your Subgraph