title: Why does this error happen? "npm run dev missing script error"
body: <p>I've been trying to follow the following tutorial:
  <a href="https://github.com/digitsensitive/phaser3-typescript/blob/master/README.md" rel="nofollow noreferrer">https://github.com/digitsensitive/phaser3-typescript/blob/master/README.md</a></p>
  
  <p>These are the steps that I had to follow </p>
  
  <p>Prerequisites
  Download and install npm with Node.js @ <a href="https://nodejs.org/en" rel="nofollow noreferrer">https://nodejs.org/en</a>
  Installing
  Select a folder, navigate to it, and clone this repository with this command-line:</p>
  
  <pre><code>git clone https://github.com/digitsensitive/phaser3-typescript.git
  </code></pre>
  
  <p>Install the dependencies with this command-line:</p>
  
  <pre><code>npm install
  </code></pre>
  
  <p>If you use yarn just replace npm with yarn</p>
  
  <p>Building and Running
  Perform a quick build (bundle.js) and start server:
  npm run dev</p>
  
  <p>I've never used node.js and npm before so I'm stumbling across some newbie mistakes. One error I get is that when I try to run npm run dev, Git bash returns the following error code:</p>
  
  <pre><code>npm ERR! missing script: dev
  
  0 info it worked if it ends with ok
  1 verbose cli [ 'C:\Program Files\nodejs\node.exe',
  1 verbose cli 'C:\Program Files\nodejs\node_modules\npm\bin\npm-cli.js',
  1 verbose cli 'run',
  1 verbose cli 'dev' ]
  2 info using npm@6.4.1
  3 info using node@v10.15.3
  4 verbose stack Error: missing script: dev
  4 verbose stack at run (C:\Program Files\nodejs\node_modules\npm\lib\run-script.js:155:19)
  4 verbose stack at C:\Program Files\nodejs\node_modules\npm\lib\run-script.js:63:5
  4 verbose stack at C:\Program Files\nodejs\node_modules\npm\node_modules\read-package-json\read-json.js:115:5
  4 verbose stack at C:\Program Files\nodejs\node_modules\npm\node_modules\read-package-json\read-json.js:418:5
  4 verbose stack at checkBinReferences_ (C:\Program Files\nodejs\node_modules\npm\node_modules\read-package-json\read-json.js:373:45)
  4 verbose stack at final (C:\Program Files\nodejs\node_modules\npm\node_modules\read-package-json\read-json.js:416:3)
  4 verbose stack at then (C:\Program Files\nodejs\node_modules\npm\node_modules\read-package-json\read-json.js:160:5)
  4 verbose stack at ReadFileContext. (C:\Program Files\nodejs\node_modules\npm\node_modules\read-package-json\read-json.js:332:20)
  4 verbose stack at ReadFileContext.callback (C:\Program Files\nodejs\node_modules\npm\node_modules\graceful-fs\graceful-fs.js:78:16)
  4 verbose stack at FSReqWrap.readFileAfterOpen [as oncomplete] (fs.js:237:13)
  5 verbose cwd C:\Users\Yassi\TEST
  6 verbose Windows_NT 10.0.17134
  </code></pre>
  
  <p>I don't know what I should be adding to my package.json file to make this work. Could anyone help me with this please?</p>
  
  <p>I made a package.json using init, but the tutorial doesn't state that I have to do this. I don't know why I should manually make a package.json file in the first place.</p>