title: How to define this paritcular typescirpt type
body: <p>I have this static property as a part of my abstract class, with a number of properties, <code>default</code> is only consistent property, all the rest could have random names</p>
  <pre><code>  public static data = {
      default: { //only this one always have 'dafault' name
        name: 'someName',
        category: ['cat 1','cat2','catN'],
        urls: ['url1', 'url2']
      },
      property1: { //can have any random name 'property3' 'xyz'
        name: 'property1',
        category: ['cat 3','cat4','cat1'],
        urls: ['url3', 'url5']
      },
      anotherThing: { //can have any random name 'oneMoreThing' 'abc'
        name: 'anotherThing',
        category: ['cat 2','catN','cat5'],
        urls: ['url5', 'url2']
      }
    };
  </code></pre>
  <p>I want to strict type that property to get a better error validation. I wonder how would you define that structure in typescript interface?</p>