Fixing to work with more recent versions of TypeScript (marcj#243)

Pauan · marcj · commit 5aa2dfcf2abc · 2018-10-16T12:11:41.000+02:00
Without this change I get this error from TypeScript:

```
Module '"node_modules/css-element-queries/src/ResizeSensor"' has no default export.

24 import ResizeSensor from "css-element-queries/src/ResizeSensor";
          ~~~~~~~~~~~~
```
diff --git a/src/ResizeSensor.d.ts b/src/ResizeSensor.d.ts
@@ -3,4 +3,4 @@ declare class ResizeSensor {
     detach(callback: Function): void;
 }
 
-export = ResizeSensor;
+export default ResizeSensor;

Original file line number	Diff line number	Diff line change
`@@ -3,4 +3,4 @@ declare class ResizeSensor {`
`3`	`3`	`detach(callback: Function): void;`
`4`	`4`	`}`
`5`	`5`
`6`		`-export = ResizeSensor;`
	`6`	`+export default ResizeSensor;`