change scroll animation effect to matrix letters

wanna implement this someday:

> For the scrolling effect, changing the boxes to the katakana like you do in the intro effect, and making them fall down the screen a bit instead of just flashing, would be good if possible to do

@fergusmeiklejohn can you google for some falling letter/character matrix effects on codepen and see if there's any small implementations that look pretty good out of the box we might be able to implement easily?

the idea is that we'd replace the side glitch lines with matrix falling characters.

if you find some please post the links here in comments, I'll choose one I like!

PS: Since we're already live, any new ticket is to be branched from `production` with branch name `pr-` and make a PR towards `production` again.
Also, remember we're using `npm` again now (as opposed to `yarn`).