Allow `--` to signal end of argument parsing

IIUC is fairly normal for tools that run other tools to use `--` to signal the end of argument parsing for the outer tool.

e.g. `node --arg-for-node -- myfile.py --arg-for-js-program`

Would it be easy/possible for hyperfine to do the same to avoid the need to quote the command line e.g.

```
$ hyperfine -- ls -la
```

Instead of:

```
$ hyperfine 'ls -la'
```
