title: How to extend `CSSProperties` in react project
body: <p>I am from the <code>javascript</code> world and am new to <code>typescript</code>. I have a react project written in <code>typescript</code>. I declare an inline style but got the below warning when I use it in a react component:</p>
  <pre><code>Type '{ color: string; fontSize: string; fontWeight: number; }' is not assignable to type 'CSSProperties'.
  </code></pre>
  <p>Below is the code for the style declaration.</p>
  <pre><code>const styles = {
      promAlert: {
          display: 'flex',
          flexDirection: 'column'
      }
  };
  </code></pre>
  <p>below is the code who uses it. And the warning comes out with this line <code>&lt;div style={styles.promAlert}&gt;</code>.</p>
  <pre><code>&lt;div style={styles.promAlert}&gt;
      {alert.substring('promotions.'.length)}
  &lt;/div&gt;
  </code></pre>
  <p>I have searched that the this may be caused by <code>CSSProperties</code> defined in react. I may need to extend this class and add more attributes on it. I wonder how I can do that in my project.</p>
  <p>Another question is why <code>CSSProperties</code> doesn't include all supported css keys.</p>