Grab the width, height, location of given locator.
Provide `width` or `height`as second param to get your desired prop.
Resumes test execution, so **should be used inside an async function with `await`** operator.

Returns an object with `x`, `y`, `width`, `height` keys.

```js
const value = await I.grabElementBoundingRect('h3');
// value is like { x: 226.5, y: 89, width: 527, height: 220 }
```

To get only one metric use second parameter:

```js
const width = await I.grabElementBoundingRect('h3', 'width');
// width == 527
```
@param {LocatorOrString} locator element located by CSS|XPath|strict locator.
@param {string=} elementSize x, y, width or height of the given element.
@returns {Promise<DOMRect>|Promise<number>} Element bounding rectangle