docs(readme): add build:dev note

Closes TrilonIO#166

Author: MarkPieszak

README.md

@@ -111,7 +111,7 @@ The project comes with the configured Launch.json files to let you just push F5
 
 ```bash
 # cd into the directory you cloned the project into
-npm install && dotnet restore
+npm install && npm run build:dev && dotnet restore
 # or yarn install
 ```