[RFC]: create ESLint rule to discourage string concatenation in benchmark descriptions

```js
// Good...
bench( pkg, function benchmark( b ) {...} );
bench( format( '%s:len=%d', pkg, len ), function benchmark( b ) {...} );

// Bad...
bench( pkg+':len='+len, function benchmark( b ) {...} );
```

This can be a warning to start given the sheer number of benchmarks using string concatenation atm.