This outputs logs to `stdout` as `DIMACS` comments:
```
c WARN: ...
c ERR: ...
```
For `Level::Info` messages, the level is not printed: this allows to
have a quiet mode for the solver by setting the level filter to
`LevelFilter::Off`.
```rust
use satlog::SatLogger;
use log::LevelFilter;
fn main() {
}
```
-