Remove unused dependencies

[emplums]

Clean up, clean up!

I ran depcheck on Primer Components and found a bunch of unused deps! Removing them 🎉

I also found a couple of other relics from the past that I removed:

• the script folder which only contains the prepack script that's not being used anymore
• the css.js file, associated dependencies, and rollup config for it. These styles were being imported in our old Next.js setup for our docs and aren't needed anymore :)

Also, react-dom was a dependency, but it only used in our tests (because some package we are using in our tests has it as a peerDep) so I moved it to devDeps. I think this is safe to do - the deploy site looks great and I double-triple checked that we aren't calling any ReactDOM methods or importing react-dom anywhere - but for some reason bundlephobia classifies it as a missing dependency 🤔 https://bundlephobia.com/result?p=@primer/components@0.0.0-acfdf18 Curious what you think @BinaryMuse

All of that cut our bundle size almost in half 🎉 It's now sitting at 49kb, down from 84.8kb.

Sidenote: If we move over to @github/details-dialog-element for our Dialog I think we can get down to ~ 28kb. Still feels semi-big but not sure what to use as a benchmark.

byeeeee! 👋👋👋

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[BinaryMuse]

but for some reason bundlephobia classifies it as a missing dependency

Weird, I'm not sure either. At first I thought it was maybe a peerDep of something? But no. Maybe bundlephobia assumes it exists when it sees React?