This refactors the front-end collateral to all live within `site` - so no `package.json` at the root.
The reason we had this initially is that the jest test run and NextJS actually require having _two_ different `tsconfig`s - Next needs `jsx:"preserve"`, while jest needs `jsx:"react"` - we were using `tsconfig`s at different levels at the hierarchy to manage this.
I changed this behavior to still use two different `tsconfig.json`s, which is mandatory - but just side-by-side in `site`.
Once that's fixed, it was easy to move everything into `site`
Follow up from: https://github.com/coder/coder/pull/118#discussion_r796244577