Support --follow-fork

## Feature Request

**Is your feature request related to a problem? Please describe.**

I'm running a test case via a subprocess, and I find that [memray provided a CLI argument for this case](https://bloomberg.github.io/memray/attach.html#cli-reference), but there is no corresponding argument for *pytest-memray*

**Describe the solution you'd like**

Hoping that there is also a CLI argument like `--memray-follow-fork` to do similar thing.

**Describe alternatives you've considered**

Maybe add a keyword argument to the mark `limit_memory` is also great.

```
@pytest.mark.limit_memory("60 KB", follow_fork = True)
```

Start by reading the linked memray CLI reference and comparing its --follow-fork behavior with pytest-memray's existing command-line options and limit_memory marker. Reproduce the subprocess test case described in the issue, then verify that the chosen interface follows forks and that the relevant pytest behavior is covered by tests.

Written by the indexing model from the issue text.