Assertions will now scroll to the element

Assertion steps will now scroll to the target element (if there is one). The reason for the change is twofold:

1. This ensures that on long pages, the screenshot will always include the element in question.
2. It also fixes an issue where the crop screenshot to element would fail on elements outside the current viewport.

We hope this makes your test output easier to use, and more helpful in diagnosing issues!