[Pages] Make the sequence footer/module navigation footer reposition to bottom of page

[Isaac_Marcus]

Problem statement:

If the document preview on a page is resized (such as making the preview of a PowerPoint taller to see more at once without going fullscreen) the sequence footer (the footer with "previous" and "next" on it) does not adjust to the new page size. It remains where it was, causing it to cover part of the content. Example: https://photos.app.goo.gl/mFAJ9Y5dBcCVsDGj9

Proposed solution:

Anchor the element to the bottom (or top, if necessary) of each page, so that it dynamically adjusts if the page size is changed.

User role(s):

instructor,student,ta,observer