I added a new option to the screenshot method to customize the color of
the box when we want to mask some elements for the screenshot.
The default color is pink `#FF00FF`, but with this new option you can
specify the color you like the most, like a nice green `#00FF00`:
```js
await page.screenshot({
mask: [page.locator('div').nth(5)],
maskColor: "#00FF00",
})
```
---------
Signed-off-by: Jasiel Guillén <darkensses@gmail.com>
Also reverted screenshot test changes from 4de14e7 as the breaking change was reverted upstream in Revert [251706@main] getComputedStyle(img).height returns string of a rounded int not a float WebKit/WebKit#1902
