fix: fixed nextjs/react hydration error when using portals (#1517)

Co-authored-by: Brandon Scott <[email protected]>

src/portal/src/Portal.js

@@ -17,18 +17,20 @@ export default class Portal extends Component {
       portalContainer.setAttribute('evergreen-portal-container', '')
       document.body.appendChild(portalContainer)
     }
+  }
 
+  componentDidMount() {
     this.el = document.createElement('div')
     portalContainer.appendChild(this.el)
+    this.forceUpdate()
   }
 
   componentWillUnmount() {
     portalContainer.removeChild(this.el)
   }
 
   render() {
-    // This fixes SSR
-    if (!canUseDom) return null
+    if (!this.el) return null
     return ReactDOM.createPortal(this.props.children, this.el)
   }
 }