Travis Van Couvering

Wish I'd seen your comment earlier @oschettler as I ended up writing exactly the same code, minus names and inconsequential style differences and then coming here to complain that the...

On Windows I had to install `cross-env` as a dev dependency: ```npm i -D cross-env``` and change `scripts.build` in `package.json` to this: ```node_modules/.bin/cross-env NODE_ENV=production \"npm run build:tailwind && sapper build\"```...

I'll look into that. `calculateTextMetrics()` is an expensive operation. Pretty busy ATM but will catch a break soon.

#14 should help. Next step will be to use [`ResizeObserver`](https://developer.mozilla.org/en-US/docs/Web/API/ResizeObserver) to monitor elements directly for size changes (instead of reclamping all watched elements when the viewport resizes).