Add installation steps for graph-cli

Added installation instructions for graph-cli.

Author: marcusrein

website/src/pages/en/subgraphs/developing/creating/graph-node-dev.mdx

@@ -13,6 +13,12 @@ Graph Node Developer Mode (GND) is a developer-friendly Graph Node runner design
 
 ## Step 1. Set Up
 
+Install `graph-cli`:
+
+```
+npm i @graphprotocol/graph-cli
+```
+
 Install `gnd` using the Graph CLI:
 
 ```