title: Can't install my custom chrome extension crx_magic_number_invalid
body: <p>I made a simple chrome extension:</p>
  
  <p>manifest.json:</p>
  
  <pre><code>{
    "name": "Layout VS Design",
    "version": "1",
    "description": "Enter the url of a image with your design at 100%",
    "background_page": "index.html",
    "browser_action": {
      "name": "Manipulate DOM",
      "icons": ["icon.png"],
      "default_icon": "icon.png"
    },
    "content_scripts": [ {
      "js": [ "jquery.min.js", "js.js" ],
      "matches": [ "http://*/*", "https://*/*"]
    }]
  }
  </code></pre>
  
  <p>The thing is that chrome won't let me install it:
  <img src="https://i.stack.imgur.com/fgku8.png" alt="enter image description here"></p>
  
  <p>The thing is I  have no idea where to set this number, Any idea what can I try?</p>