Feature: Have a command to bootstrap new tests

### Feature description

Rather than relying on existing examples, or reading documentation, I think it'd be pretty sweet having a specific `benchi` command to bootstrap a new directory structure so it's easier to add new tests.

Example:

```bash
benchi init pg-to-kafka --path ./my-tests/
> Creating configuration file in `./my-tests/benchi.yml`
...
```