Clean-up the codebase and the tests
Release a first version under the terms of the MPL 2.0
Fix build for recent version of syn

It looks like the `export` module is no longer a thing, so we directly
use `proc-macro2` insead.
Turn typed-urls-tera into a feature and introduce the actix feature
Derive Serialize implementation
Remove the Routing trait in favor of the more logical TypedUrl
Introduce typed-urls-tera
Make [to_string] public
Rename into typed-urls