Feature request: delete keys from a Map by selector

I found myself wanting to do something like this

```go
m := objx.New(data)
m.Delete("foo.bar")
```

But didn't see any way of doing that without casting back to `map[string]any` and doing it myself. It would be nice to have this. I worked around it by using `m.Set("foo.bar", nil)`, but that may not work for other peoples' use cases.