- Remove unused CSS files
- Set up the `.wasm` files to be automatically copied in
- `sql-wasm-debug.wasm` is removed entirely since we never use the
debug/dev build of sql.js. This reduces the app download size by 1MB on
the server side. It may be worth enabling the debug build automatically
in the future?

~based on #1114~

This brings its build process up to date with the rest of the project.
We can now use Node 20 to build successfully.

Closes #918

These files will be automatically recreated by `yarn build:api`,
`yarn build:browser`, and `yarn start:browser`, so we don’t need
them in the repo.

Co-authored-by: Tom French <15848336+TomAFrench@users.noreply.github.com>