Update README.md

README.md

@@ -23,6 +23,7 @@ Form Labeling Tool requires [NodeJS (>= 10.x, Dubnium) and NPM](https://github.c
    ```bash
     git clone https://github.com/Microsoft/OCR-Form-Tools.git
     cd OCR-Form-Tools
+    npm install
     npm run build
     npm run react-start
    ```