Now that Zui v1.0.0 is out, the animated GIFs that have been used for install guidance are due for an update, which is covered in this PR. I've also expanded the Filesystem Paths article with the separate Windows guidance for the single-user & all-user install types. Finally, I've dropped the link to the old Brim demo video since Zui is now different enough that I expect a new user would be confused by it if looking at it side-by-side next to current Zui. I hope to soon create some new entry-level Zui demo videos that could take its place.

While video editing is potentially time consuming, since these videos are short and I have the originals in Camtasia, making edits would be pretty easy. Reviews should not be shy if you have ideas for improvement.

So you can easily see the animated GIFs and the rendered docs pages in their updated forms, I've done a deployment of what's in this branch to a staging site in a personal Netlify at https://jocular-choux-3cf6d8.netlify.app/docs.

Closes #2706