Reticulate support F1 to show help

## Describe the issue:

Currently if you have a python object in the R session using reticulate eg:

```
np <- reticulate::import("numpy")
np$su|m
```

`|` indicates the cursor position. If we then press F1, we see the helpm documentation for `base::sum`.
We should see the the documentation for `np$sum`.
