Resize the viewport to <width> x <height> then save a full-page screenshot.
Then (I |we )*save fullscreen (\d+) x (\d+) screenshot
Example #1: Then I save fullscreen 1440 x 900 screenshot
Example #2: Then we save fullscreen 1200 x 800 screenshot
Example #3: Then save fullscreen 375 x 667 screenshot
Example #4
Given I am on "/about-us"
Then I save fullscreen 1440 x 900 screenshot
Example #5:
Given I am on "/long-article"
Then I save fullscreen 1440 x 900 screenshot