New video animation for home page

[jaronheard]

What

A new video animation needs to be created and added to the HomePage component in the 2018 package.

Why

The current home page animation was done in a rush before Demo Day and doesn't adequately represent Civic Platform functionality.

Per @catnik, an ideal home page animation would show something like the following sequence:

• filtering a list of cards
• navigating to full card view
• interacting with data visualization
• sharing / embedding a card

Some of the interfaces involved in this don't show particularly well, at the moment, so follow up issues could be generated to capture the improvements needed.

However, any animation that improves on the current one would be accepted.

When

Not time sensitive, but the sooner the better

[jaronheard]

If possible, implement this comment on #1043 as part of new animation

An easy solution would be to who the white screen at the end of the video rather than the beginning, so we don't even have to implement the poster.