Add scrolling animate on sidebar hide

[Matt-Yorkley]

What? Why?

Closes #5765

Adds sliding animation on cart sidebar close.

What should we test?

Cart sidebar slides out when closed.

Release notes

Added sliding animation on cart sidebar close

[luisramos0]

Very simple code change, moving to test ready with one approval.

[daniellemoorhead]

Good news: Slides back in now, good job 👍

Bad news: I've noticed strange things happening on desktop and tablet (and mobile but the cart covers the whole screen so not as noticeable) that's also on production.

• When cart opens on Desktop (Mac/Chrome + Safari and Windows 10/Chrome) the page content jumps a few pixels to the right (on any page) and then when you shut it the page jumps back to the original position.
• On mobile and tablet the sticky search/filter bar disappears whenever you open the cart. It doesn't disappear when the sticky factor isn't engaged.

I'm going to log bugs for these 2 things to be fixed - yep, they're not critical, but if we're going to implement these design changes then I reckon we should be making it look right the first time around, especially on this outward facing part of the app.

[luisramos0]

@daniellemoorhead from what you write it looks like this PR is ready to go but you havent moved it to Ready to Go. Can I merge?