Paint issues for the header

First, thanks for putting together such an excellent resource ✨.

I created this issue because I saw the header jumping while scrolling as shown below...

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This element triggers repaints on scroll **only on non-retina displays**, so please consider moving it to its layer.

I came across [this Stack Overflow question](https://stackoverflow.com/a/32744881) that links to [this bug](https://bugs.chromium.org/p/chromium/issues/detail?id=514303) explaining this behavior in devices with different pixels ratio.


As a side improvement, the [`ScrollContainerDiv`](https://github.com/GoogleChromeLabs/progressive-tooling/blob/master/src/components/card-scroll/card-scroll.style.js#L21) component should also be moved to its layer to avoid scrolling performance issues.