Prefer not to use "export default"

I'd prefer to use "export [name]" instead of "export default" and "module.exports =". The main reason is that our library can give reasonable naming expectations to users of this library, which improves the ecosystem's legibility.

For example, if `user A` says `import braid from "@josephg/braid-server` in their code, while `user B` says `import stream from "@josephg/braid-server"` this adds unnecessary confusion to newcomers looking across code bases that use our library.

As far as I know, there is very little downside to named exports--if a user is particularly opinionated and really wants to override our naming expections, they can always reach for `import { stream as braid } from "@josephg/braid-server` or `const braid = require("@josephg/braid-server").stream` if they want to.