As a Wikipedia visitor (dot org),
I want banners not to show if the viewport is too small,
so that my reading experience is not being disrupted.

Acceptance Criteria:

• If a banner would cause the Wikipedia logo to be outside of the viewport, it will not be displayed.
• If a banner is not being displayed, loading the banner does not trigger a banner impression.
• If a banner is too big, a too-big request is tracked

Background:
This is an outcome of the workshop regarding the fundraising principles. We already identified the problem, that the viewport of some users' browsers is too small to display our banners. A viewport is considered "too small", when - due to the size of a banner - the Wikipedia logo is not being displayed completely.

The measuring is already being done. Currently, we only track these cases and do not take any action.

We do want to prevent the banner from being displayed and then hidden again, so we need to implement a reliable way to measure the banner size (and the remaining space within the viewport) before it is shown to a user.