Migration of jsx files to tsx 3 (#851)

This is in continue to:
- #850
- #848

The last files should be converted as part of this PR, there are only a
handful left.

src/components/IconLayer.tsx

@@ -10,6 +10,7 @@ import IconMissing from './IconMissing'
 type IconLayerProps = {
   type: string
   style?: object
+  className?: string
 };
 
 export default class IconLayer extends React.Component<IconLayerProps> {