Update part3a.md

Explain why we need to add `run`

Author: MarcGuay

src/content/3/en/part3a.md

@@ -420,7 +420,7 @@ We can now start the server in development mode with the command:
 npm run dev
 ```
 
-Unlike with the <i>start</i> and <i>test</i> scripts, we also have to add <i>run</i> to the command.
+Unlike with the <i>start</i> and <i>test</i> scripts, we also have to add <i>run</i> to the command because it is a non-native script.
 
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