[feature request] rewrite path

I love using it to mock web apps using HTML pages.
However I'd like to strip the `.html` extension in URL path.

E.g. instead of requesting `/home.html` to serve local `./home.html`, I'd like to request `/home`.

I could achieve that with a simple path rewrite, e.g. a CLI option `--path-rewrite` with a regex.

```bash
simple-http-server --path-rewrite='s/*.html$//'
```